Merge branch 'ms/core-icase-doc'
[gitweb.git] / sequencer.c
index e0e66b987b27072da4aea6304a565ab708be91e4..03c47405fbf2c1896d4a1d38ef9f204518d7e92d 100644 (file)
@@ -1,13 +1,14 @@
 #include "cache.h"
 #include "config.h"
 #include "lockfile.h"
-#include "sequencer.h"
 #include "dir.h"
+#include "object-store.h"
 #include "object.h"
 #include "commit.h"
+#include "sequencer.h"
 #include "tag.h"
 #include "run-command.h"
-#include "exec_cmd.h"
+#include "exec-cmd.h"
 #include "utf8.h"
 #include "cache-tree.h"
 #include "diff.h"
 #include "trailer.h"
 #include "log-tree.h"
 #include "wt-status.h"
+#include "hashmap.h"
+#include "notes-utils.h"
+#include "sigchain.h"
+#include "unpack-trees.h"
+#include "worktree.h"
+#include "oidmap.h"
+#include "oidset.h"
+#include "commit-slab.h"
+#include "alias.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
 const char sign_off_header[] = "Signed-off-by: ";
 static const char cherry_picked_prefix[] = "(cherry picked from commit ";
 
+GIT_PATH_FUNC(git_path_commit_editmsg, "COMMIT_EDITMSG")
+
 GIT_PATH_FUNC(git_path_seq_dir, "sequencer")
 
 static GIT_PATH_FUNC(git_path_todo_file, "sequencer/todo")
@@ -69,13 +81,6 @@ static GIT_PATH_FUNC(rebase_path_message, "rebase-merge/message")
  * previous commit and from the first squash/fixup commit are written
  * to it. The commit message for each subsequent squash/fixup commit
  * is appended to the file as it is processed.
- *
- * The first line of the file is of the form
- *     # This is a combination of $count commits.
- * where $count is the number of commits whose messages have been
- * written to the file so far (including the initial "pick" commit).
- * Each time that a commit message is processed, this line is read and
- * updated. It is deleted just before the combined commit is made.
  */
 static GIT_PATH_FUNC(rebase_path_squash_msg, "rebase-merge/message-squash")
 /*
@@ -86,6 +91,11 @@ static GIT_PATH_FUNC(rebase_path_squash_msg, "rebase-merge/message-squash")
  * commit without opening the editor.)
  */
 static GIT_PATH_FUNC(rebase_path_fixup_msg, "rebase-merge/message-fixup")
+/*
+ * This file contains the list fixup/squash commands that have been
+ * accumulated into message-fixup or message-squash so far.
+ */
+static GIT_PATH_FUNC(rebase_path_current_fixups, "rebase-merge/current-fixups")
 /*
  * A script to set the GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, and
  * GIT_AUTHOR_DATE that will be used for the commit that is currently
@@ -115,6 +125,19 @@ static GIT_PATH_FUNC(rebase_path_stopped_sha, "rebase-merge/stopped-sha")
 static GIT_PATH_FUNC(rebase_path_rewritten_list, "rebase-merge/rewritten-list")
 static GIT_PATH_FUNC(rebase_path_rewritten_pending,
        "rebase-merge/rewritten-pending")
+
+/*
+ * The path of the file containig the OID of the "squash onto" commit, i.e.
+ * the dummy commit used for `reset [new root]`.
+ */
+static GIT_PATH_FUNC(rebase_path_squash_onto, "rebase-merge/squash-onto")
+
+/*
+ * The path of the file listing refs that need to be deleted after the rebase
+ * finishes. This is used by the `label` command to record the need for cleanup.
+ */
+static GIT_PATH_FUNC(rebase_path_refs_to_delete, "rebase-merge/refs-to-delete")
+
 /*
  * The following files are written by git-rebase just after parsing the
  * command-line (and are only consumed, not modified, by the sequencer).
@@ -122,6 +145,7 @@ static GIT_PATH_FUNC(rebase_path_rewritten_pending,
 static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
 static GIT_PATH_FUNC(rebase_path_orig_head, "rebase-merge/orig-head")
 static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
+static GIT_PATH_FUNC(rebase_path_signoff, "rebase-merge/signoff")
 static GIT_PATH_FUNC(rebase_path_head_name, "rebase-merge/head-name")
 static GIT_PATH_FUNC(rebase_path_onto, "rebase-merge/onto")
 static GIT_PATH_FUNC(rebase_path_autostash, "rebase-merge/autostash")
@@ -129,6 +153,52 @@ static GIT_PATH_FUNC(rebase_path_strategy, "rebase-merge/strategy")
 static GIT_PATH_FUNC(rebase_path_strategy_opts, "rebase-merge/strategy_opts")
 static GIT_PATH_FUNC(rebase_path_allow_rerere_autoupdate, "rebase-merge/allow_rerere_autoupdate")
 
+static int git_sequencer_config(const char *k, const char *v, void *cb)
+{
+       struct replay_opts *opts = cb;
+       int status;
+
+       if (!strcmp(k, "commit.cleanup")) {
+               const char *s;
+
+               status = git_config_string(&s, k, v);
+               if (status)
+                       return status;
+
+               if (!strcmp(s, "verbatim"))
+                       opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
+               else if (!strcmp(s, "whitespace"))
+                       opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
+               else if (!strcmp(s, "strip"))
+                       opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_ALL;
+               else if (!strcmp(s, "scissors"))
+                       opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
+               else
+                       warning(_("invalid commit message cleanup mode '%s'"),
+                                 s);
+
+               free((char *)s);
+               return status;
+       }
+
+       if (!strcmp(k, "commit.gpgsign")) {
+               opts->gpg_sign = git_config_bool(k, v) ? xstrdup("") : NULL;
+               return 0;
+       }
+
+       status = git_gpg_config(k, v, NULL);
+       if (status)
+               return status;
+
+       return git_diff_basic_config(k, v, NULL);
+}
+
+void sequencer_init_config(struct replay_opts *opts)
+{
+       opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
+       git_config(git_sequencer_config, opts);
+}
+
 static inline int is_rebase_i(const struct replay_opts *opts)
 {
        return opts->action == REPLAY_INTERACTIVE_REBASE;
@@ -194,18 +264,35 @@ static const char *gpg_sign_opt_quoted(struct replay_opts *opts)
 
 int sequencer_remove_state(struct replay_opts *opts)
 {
-       struct strbuf dir = STRBUF_INIT;
+       struct strbuf buf = STRBUF_INIT;
        int i;
 
+       if (is_rebase_i(opts) &&
+           strbuf_read_file(&buf, rebase_path_refs_to_delete(), 0) > 0) {
+               char *p = buf.buf;
+               while (*p) {
+                       char *eol = strchr(p, '\n');
+                       if (eol)
+                               *eol = '\0';
+                       if (delete_ref("(rebase -i) cleanup", p, NULL, 0) < 0)
+                               warning(_("could not delete '%s'"), p);
+                       if (!eol)
+                               break;
+                       p = eol + 1;
+               }
+       }
+
        free(opts->gpg_sign);
        free(opts->strategy);
        for (i = 0; i < opts->xopts_nr; i++)
                free(opts->xopts[i]);
        free(opts->xopts);
+       strbuf_release(&opts->current_fixups);
 
-       strbuf_addf(&dir, "%s", get_dir(opts));
-       remove_dir_recursively(&dir, 0);
-       strbuf_release(&dir);
+       strbuf_reset(&buf);
+       strbuf_addstr(&buf, get_dir(opts));
+       remove_dir_recursively(&buf, 0);
+       strbuf_release(&buf);
 
        return 0;
 }
@@ -232,7 +319,7 @@ struct commit_message {
 
 static const char *short_commit_name(struct commit *commit)
 {
-       return find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV);
+       return find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV);
 }
 
 static int get_message(struct commit *commit, struct commit_message *out)
@@ -271,7 +358,7 @@ static void print_advice(int show_hint, struct replay_opts *opts)
                 * (typically rebase --interactive) wants to take care
                 * of the commit itself so remove CHERRY_PICK_HEAD
                 */
-               unlink(git_path_cherry_pick_head());
+               unlink(git_path_cherry_pick_head(the_repository));
                return;
        }
 
@@ -289,23 +376,23 @@ static void print_advice(int show_hint, struct replay_opts *opts)
 static int write_message(const void *buf, size_t len, const char *filename,
                         int append_eol)
 {
-       static struct lock_file msg_file;
+       struct lock_file msg_file = LOCK_INIT;
 
        int msg_fd = hold_lock_file_for_update(&msg_file, filename, 0);
        if (msg_fd < 0)
                return error_errno(_("could not lock '%s'"), filename);
        if (write_in_full(msg_fd, buf, len) < 0) {
+               error_errno(_("could not write to '%s'"), filename);
                rollback_lock_file(&msg_file);
-               return error_errno(_("could not write to '%s'"), filename);
+               return -1;
        }
        if (append_eol && write(msg_fd, "\n", 1) < 0) {
+               error_errno(_("could not write eol to '%s'"), filename);
                rollback_lock_file(&msg_file);
-               return error_errno(_("could not write eol to '%s'"), filename);
-       }
-       if (commit_lock_file(&msg_file) < 0) {
-               rollback_lock_file(&msg_file);
-               return error(_("failed to finalize '%s'."), filename);
+               return -1;
        }
+       if (commit_lock_file(&msg_file) < 0)
+               return error(_("failed to finalize '%s'"), filename);
 
        return 0;
 }
@@ -346,7 +433,7 @@ static int read_oneliner(struct strbuf *buf,
 
 static struct tree *empty_tree(void)
 {
-       return lookup_tree(&empty_tree_oid);
+       return lookup_tree(the_hash_algo->empty_tree);
 }
 
 static int error_dirty_index(struct replay_opts *opts)
@@ -392,7 +479,8 @@ static int fast_forward_to(const struct object_id *to, const struct object_id *f
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
            ref_transaction_update(transaction, "HEAD",
-                                  to->hash, unborn ? null_sha1 : from->hash,
+                                  to, unborn && !is_rebase_i(opts) ?
+                                  &null_oid : from,
                                   0, sb.buf, &err) ||
            ref_transaction_commit(transaction, &err)) {
                ref_transaction_free(transaction);
@@ -435,9 +523,10 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
        struct tree *result, *next_tree, *base_tree, *head_tree;
        int clean;
        char **xopt;
-       static struct lock_file index_lock;
+       struct lock_file index_lock = LOCK_INIT;
 
-       hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
+       if (hold_locked_index(&index_lock, LOCK_REPORT_ON_ERROR) < 0)
+               return -1;
 
        read_cache();
 
@@ -447,10 +536,11 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
        o.branch2 = next ? next_label : "(empty tree)";
        if (is_rebase_i(opts))
                o.buffer_output = 2;
+       o.show_rename_progress = 1;
 
        head_tree = parse_tree_indirect(head);
-       next_tree = next ? next->tree : empty_tree();
-       base_tree = base ? base->tree : empty_tree();
+       next_tree = next ? get_commit_tree(next) : empty_tree();
+       base_tree = base ? get_commit_tree(base) : empty_tree();
 
        for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
                parse_merge_opt(&o, *xopt);
@@ -461,21 +551,20 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
        if (is_rebase_i(opts) && clean <= 0)
                fputs(o.obuf.buf, stdout);
        strbuf_release(&o.obuf);
-       if (clean < 0)
+       diff_warn_rename_limit("merge.renamelimit", o.needed_rename_limit, 0);
+       if (clean < 0) {
+               rollback_lock_file(&index_lock);
                return clean;
+       }
 
-       if (active_cache_changed &&
-           write_locked_index(&the_index, &index_lock, COMMIT_LOCK))
+       if (write_locked_index(&the_index, &index_lock,
+                              COMMIT_LOCK | SKIP_IF_UNCHANGED))
                /*
                 * TRANSLATORS: %s will be "revert", "cherry-pick" or
                 * "rebase -i".
                 */
                return error(_("%s: Unable to write new index file"),
                        _(action_name(opts)));
-       rollback_lock_file(&index_lock);
-
-       if (opts->signoff)
-               append_signoff(msgbuf, 0, 0);
 
        if (!clean)
                append_conflicts_hint(msgbuf);
@@ -483,13 +572,27 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
        return !clean;
 }
 
+static struct object_id *get_cache_tree_oid(void)
+{
+       if (!active_cache_tree)
+               active_cache_tree = cache_tree();
+
+       if (!cache_tree_fully_valid(active_cache_tree))
+               if (cache_tree_update(&the_index, 0)) {
+                       error(_("unable to update cache tree"));
+                       return NULL;
+               }
+
+       return &active_cache_tree->oid;
+}
+
 static int is_index_unchanged(void)
 {
-       struct object_id head_oid;
+       struct object_id head_oid, *cache_tree_oid;
        struct commit *head_commit;
 
-       if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_oid.hash, NULL))
-               return error(_("could not resolve HEAD commit\n"));
+       if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
+               return error(_("could not resolve HEAD commit"));
 
        head_commit = lookup_commit(&head_oid);
 
@@ -504,15 +607,10 @@ static int is_index_unchanged(void)
        if (parse_commit(head_commit))
                return -1;
 
-       if (!active_cache_tree)
-               active_cache_tree = cache_tree();
-
-       if (!cache_tree_fully_valid(active_cache_tree))
-               if (cache_tree_update(&the_index, 0))
-                       return error(_("unable to update cache tree\n"));
+       if (!(cache_tree_oid = get_cache_tree_oid()))
+               return -1;
 
-       return !oidcmp(&active_cache_tree->oid,
-                      &head_commit->tree->object.oid);
+       return !oidcmp(cache_tree_oid, get_commit_tree_oid(head_commit));
 }
 
 static int write_author_script(const char *message)
@@ -592,6 +690,64 @@ static int read_env_script(struct argv_array *env)
        return 0;
 }
 
+static char *get_author(const char *message)
+{
+       size_t len;
+       const char *a;
+
+       a = find_commit_header(message, "author", &len);
+       if (a)
+               return xmemdupz(a, len);
+
+       return NULL;
+}
+
+/* Read author-script and return an ident line (author <email> timestamp) */
+static const char *read_author_ident(struct strbuf *buf)
+{
+       const char *keys[] = {
+               "GIT_AUTHOR_NAME=", "GIT_AUTHOR_EMAIL=", "GIT_AUTHOR_DATE="
+       };
+       char *in, *out, *eol;
+       int i = 0, len;
+
+       if (strbuf_read_file(buf, rebase_path_author_script(), 256) <= 0)
+               return NULL;
+
+       /* dequote values and construct ident line in-place */
+       for (in = out = buf->buf; i < 3 && in - buf->buf < buf->len; i++) {
+               if (!skip_prefix(in, keys[i], (const char **)&in)) {
+                       warning("could not parse '%s' (looking for '%s'",
+                               rebase_path_author_script(), keys[i]);
+                       return NULL;
+               }
+
+               eol = strchrnul(in, '\n');
+               *eol = '\0';
+               sq_dequote(in);
+               len = strlen(in);
+
+               if (i > 0) /* separate values by spaces */
+                       *(out++) = ' ';
+               if (i == 1) /* email needs to be surrounded by <...> */
+                       *(out++) = '<';
+               memmove(out, in, len);
+               out += len;
+               if (i == 1) /* email needs to be surrounded by <...> */
+                       *(out++) = '>';
+               in = eol + 1;
+       }
+
+       if (i < 3) {
+               warning("could not parse '%s' (looking for '%s')",
+                       rebase_path_author_script(), keys[i]);
+               return NULL;
+       }
+
+       buf->len = out - buf->buf;
+       return buf->buf;
+}
+
 static const char staged_changes_advice[] =
 N_("you have staged changes in your working tree\n"
 "If these changes are meant to be squashed into the previous commit, run:\n"
@@ -611,6 +767,7 @@ N_("you have staged changes in your working tree\n"
 #define AMEND_MSG   (1<<2)
 #define CLEANUP_MSG (1<<3)
 #define VERIFY_MSG  (1<<4)
+#define CREATE_ROOT_COMMIT (1<<5)
 
 /*
  * If we are cherry-pick, and if the merge did not result in
@@ -630,6 +787,40 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
        struct child_process cmd = CHILD_PROCESS_INIT;
        const char *value;
 
+       if ((flags & CREATE_ROOT_COMMIT) && !(flags & AMEND_MSG)) {
+               struct strbuf msg = STRBUF_INIT, script = STRBUF_INIT;
+               const char *author = is_rebase_i(opts) ?
+                       read_author_ident(&script) : NULL;
+               struct object_id root_commit, *cache_tree_oid;
+               int res = 0;
+
+               if (!defmsg)
+                       BUG("root commit without message");
+
+               if (!(cache_tree_oid = get_cache_tree_oid()))
+                       res = -1;
+
+               if (!res)
+                       res = strbuf_read_file(&msg, defmsg, 0);
+
+               if (res <= 0)
+                       res = error_errno(_("could not read '%s'"), defmsg);
+               else
+                       res = commit_tree(msg.buf, msg.len, cache_tree_oid,
+                                         NULL, &root_commit, author,
+                                         opts->gpg_sign);
+
+               strbuf_release(&msg);
+               strbuf_release(&script);
+               if (!res) {
+                       update_ref(NULL, "CHERRY_PICK_HEAD", &root_commit, NULL,
+                                  REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR);
+                       res = update_ref(NULL, "HEAD", &root_commit, NULL, 0,
+                                        UPDATE_REFS_MSG_ON_ERR);
+               }
+               return res < 0 ? error(_("writing root commit")) : 0;
+       }
+
        cmd.git_cmd = 1;
 
        if (is_rebase_i(opts)) {
@@ -654,10 +845,10 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
                argv_array_push(&cmd.args, "--amend");
        if (opts->gpg_sign)
                argv_array_pushf(&cmd.args, "-S%s", opts->gpg_sign);
-       if (opts->signoff)
-               argv_array_push(&cmd.args, "-s");
        if (defmsg)
                argv_array_pushl(&cmd.args, "-F", defmsg, NULL);
+       else if (!(flags & EDIT_MSG))
+               argv_array_pushl(&cmd.args, "-C", "HEAD", NULL);
        if ((flags & CLEANUP_MSG))
                argv_array_push(&cmd.args, "--cleanup=strip");
        if ((flags & EDIT_MSG))
@@ -690,24 +881,482 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
        return run_command(&cmd);
 }
 
+static int rest_is_empty(const struct strbuf *sb, int start)
+{
+       int i, eol;
+       const char *nl;
+
+       /* Check if the rest is just whitespace and Signed-off-by's. */
+       for (i = start; i < sb->len; i++) {
+               nl = memchr(sb->buf + i, '\n', sb->len - i);
+               if (nl)
+                       eol = nl - sb->buf;
+               else
+                       eol = sb->len;
+
+               if (strlen(sign_off_header) <= eol - i &&
+                   starts_with(sb->buf + i, sign_off_header)) {
+                       i = eol;
+                       continue;
+               }
+               while (i < eol)
+                       if (!isspace(sb->buf[i++]))
+                               return 0;
+       }
+
+       return 1;
+}
+
+/*
+ * Find out if the message in the strbuf contains only whitespace and
+ * Signed-off-by lines.
+ */
+int message_is_empty(const struct strbuf *sb,
+                    enum commit_msg_cleanup_mode cleanup_mode)
+{
+       if (cleanup_mode == COMMIT_MSG_CLEANUP_NONE && sb->len)
+               return 0;
+       return rest_is_empty(sb, 0);
+}
+
+/*
+ * See if the user edited the message in the editor or left what
+ * was in the template intact
+ */
+int template_untouched(const struct strbuf *sb, const char *template_file,
+                      enum commit_msg_cleanup_mode cleanup_mode)
+{
+       struct strbuf tmpl = STRBUF_INIT;
+       const char *start;
+
+       if (cleanup_mode == COMMIT_MSG_CLEANUP_NONE && sb->len)
+               return 0;
+
+       if (!template_file || strbuf_read_file(&tmpl, template_file, 0) <= 0)
+               return 0;
+
+       strbuf_stripspace(&tmpl, cleanup_mode == COMMIT_MSG_CLEANUP_ALL);
+       if (!skip_prefix(sb->buf, tmpl.buf, &start))
+               start = sb->buf;
+       strbuf_release(&tmpl);
+       return rest_is_empty(sb, start - sb->buf);
+}
+
+int update_head_with_reflog(const struct commit *old_head,
+                           const struct object_id *new_head,
+                           const char *action, const struct strbuf *msg,
+                           struct strbuf *err)
+{
+       struct ref_transaction *transaction;
+       struct strbuf sb = STRBUF_INIT;
+       const char *nl;
+       int ret = 0;
+
+       if (action) {
+               strbuf_addstr(&sb, action);
+               strbuf_addstr(&sb, ": ");
+       }
+
+       nl = strchr(msg->buf, '\n');
+       if (nl) {
+               strbuf_add(&sb, msg->buf, nl + 1 - msg->buf);
+       } else {
+               strbuf_addbuf(&sb, msg);
+               strbuf_addch(&sb, '\n');
+       }
+
+       transaction = ref_transaction_begin(err);
+       if (!transaction ||
+           ref_transaction_update(transaction, "HEAD", new_head,
+                                  old_head ? &old_head->object.oid : &null_oid,
+                                  0, sb.buf, err) ||
+           ref_transaction_commit(transaction, err)) {
+               ret = -1;
+       }
+       ref_transaction_free(transaction);
+       strbuf_release(&sb);
+
+       return ret;
+}
+
+static int run_rewrite_hook(const struct object_id *oldoid,
+                           const struct object_id *newoid)
+{
+       struct child_process proc = CHILD_PROCESS_INIT;
+       const char *argv[3];
+       int code;
+       struct strbuf sb = STRBUF_INIT;
+
+       argv[0] = find_hook("post-rewrite");
+       if (!argv[0])
+               return 0;
+
+       argv[1] = "amend";
+       argv[2] = NULL;
+
+       proc.argv = argv;
+       proc.in = -1;
+       proc.stdout_to_stderr = 1;
+
+       code = start_command(&proc);
+       if (code)
+               return code;
+       strbuf_addf(&sb, "%s %s\n", oid_to_hex(oldoid), oid_to_hex(newoid));
+       sigchain_push(SIGPIPE, SIG_IGN);
+       write_in_full(proc.in, sb.buf, sb.len);
+       close(proc.in);
+       strbuf_release(&sb);
+       sigchain_pop(SIGPIPE);
+       return finish_command(&proc);
+}
+
+void commit_post_rewrite(const struct commit *old_head,
+                        const struct object_id *new_head)
+{
+       struct notes_rewrite_cfg *cfg;
+
+       cfg = init_copy_notes_for_rewrite("amend");
+       if (cfg) {
+               /* we are amending, so old_head is not NULL */
+               copy_note_for_rewrite(cfg, &old_head->object.oid, new_head);
+               finish_copy_notes_for_rewrite(cfg, "Notes added by 'git commit --amend'");
+       }
+       run_rewrite_hook(&old_head->object.oid, new_head);
+}
+
+static int run_prepare_commit_msg_hook(struct strbuf *msg, const char *commit)
+{
+       struct argv_array hook_env = ARGV_ARRAY_INIT;
+       int ret;
+       const char *name;
+
+       name = git_path_commit_editmsg();
+       if (write_message(msg->buf, msg->len, name, 0))
+               return -1;
+
+       argv_array_pushf(&hook_env, "GIT_INDEX_FILE=%s", get_index_file());
+       argv_array_push(&hook_env, "GIT_EDITOR=:");
+       if (commit)
+               ret = run_hook_le(hook_env.argv, "prepare-commit-msg", name,
+                                 "commit", commit, NULL);
+       else
+               ret = run_hook_le(hook_env.argv, "prepare-commit-msg", name,
+                                 "message", NULL);
+       if (ret)
+               ret = error(_("'prepare-commit-msg' hook failed"));
+       argv_array_clear(&hook_env);
+
+       return ret;
+}
+
+static const char implicit_ident_advice_noconfig[] =
+N_("Your name and email address were configured automatically based\n"
+"on your username and hostname. Please check that they are accurate.\n"
+"You can suppress this message by setting them explicitly. Run the\n"
+"following command and follow the instructions in your editor to edit\n"
+"your configuration file:\n"
+"\n"
+"    git config --global --edit\n"
+"\n"
+"After doing this, you may fix the identity used for this commit with:\n"
+"\n"
+"    git commit --amend --reset-author\n");
+
+static const char implicit_ident_advice_config[] =
+N_("Your name and email address were configured automatically based\n"
+"on your username and hostname. Please check that they are accurate.\n"
+"You can suppress this message by setting them explicitly:\n"
+"\n"
+"    git config --global user.name \"Your Name\"\n"
+"    git config --global user.email you@example.com\n"
+"\n"
+"After doing this, you may fix the identity used for this commit with:\n"
+"\n"
+"    git commit --amend --reset-author\n");
+
+static const char *implicit_ident_advice(void)
+{
+       char *user_config = expand_user_path("~/.gitconfig", 0);
+       char *xdg_config = xdg_config_home("config");
+       int config_exists = file_exists(user_config) || file_exists(xdg_config);
+
+       free(user_config);
+       free(xdg_config);
+
+       if (config_exists)
+               return _(implicit_ident_advice_config);
+       else
+               return _(implicit_ident_advice_noconfig);
+
+}
+
+void print_commit_summary(const char *prefix, const struct object_id *oid,
+                         unsigned int flags)
+{
+       struct rev_info rev;
+       struct commit *commit;
+       struct strbuf format = STRBUF_INIT;
+       const char *head;
+       struct pretty_print_context pctx = {0};
+       struct strbuf author_ident = STRBUF_INIT;
+       struct strbuf committer_ident = STRBUF_INIT;
+
+       commit = lookup_commit(oid);
+       if (!commit)
+               die(_("couldn't look up newly created commit"));
+       if (parse_commit(commit))
+               die(_("could not parse newly created commit"));
+
+       strbuf_addstr(&format, "format:%h] %s");
+
+       format_commit_message(commit, "%an <%ae>", &author_ident, &pctx);
+       format_commit_message(commit, "%cn <%ce>", &committer_ident, &pctx);
+       if (strbuf_cmp(&author_ident, &committer_ident)) {
+               strbuf_addstr(&format, "\n Author: ");
+               strbuf_addbuf_percentquote(&format, &author_ident);
+       }
+       if (flags & SUMMARY_SHOW_AUTHOR_DATE) {
+               struct strbuf date = STRBUF_INIT;
+
+               format_commit_message(commit, "%ad", &date, &pctx);
+               strbuf_addstr(&format, "\n Date: ");
+               strbuf_addbuf_percentquote(&format, &date);
+               strbuf_release(&date);
+       }
+       if (!committer_ident_sufficiently_given()) {
+               strbuf_addstr(&format, "\n Committer: ");
+               strbuf_addbuf_percentquote(&format, &committer_ident);
+               if (advice_implicit_identity) {
+                       strbuf_addch(&format, '\n');
+                       strbuf_addstr(&format, implicit_ident_advice());
+               }
+       }
+       strbuf_release(&author_ident);
+       strbuf_release(&committer_ident);
+
+       init_revisions(&rev, prefix);
+       setup_revisions(0, NULL, &rev, NULL);
+
+       rev.diff = 1;
+       rev.diffopt.output_format =
+               DIFF_FORMAT_SHORTSTAT | DIFF_FORMAT_SUMMARY;
+
+       rev.verbose_header = 1;
+       rev.show_root_diff = 1;
+       get_commit_format(format.buf, &rev);
+       rev.always_show_header = 0;
+       rev.diffopt.detect_rename = DIFF_DETECT_RENAME;
+       rev.diffopt.break_opt = 0;
+       diff_setup_done(&rev.diffopt);
+
+       head = resolve_ref_unsafe("HEAD", 0, NULL, NULL);
+       if (!head)
+               die_errno(_("unable to resolve HEAD after creating commit"));
+       if (!strcmp(head, "HEAD"))
+               head = _("detached HEAD");
+       else
+               skip_prefix(head, "refs/heads/", &head);
+       printf("[%s%s ", head, (flags & SUMMARY_INITIAL_COMMIT) ?
+                                               _(" (root-commit)") : "");
+
+       if (!log_tree_commit(&rev, commit)) {
+               rev.always_show_header = 1;
+               rev.use_terminator = 1;
+               log_tree_commit(&rev, commit);
+       }
+
+       strbuf_release(&format);
+}
+
+static int parse_head(struct commit **head)
+{
+       struct commit *current_head;
+       struct object_id oid;
+
+       if (get_oid("HEAD", &oid)) {
+               current_head = NULL;
+       } else {
+               current_head = lookup_commit_reference(&oid);
+               if (!current_head)
+                       return error(_("could not parse HEAD"));
+               if (oidcmp(&oid, &current_head->object.oid)) {
+                       warning(_("HEAD %s is not a commit!"),
+                               oid_to_hex(&oid));
+               }
+               if (parse_commit(current_head))
+                       return error(_("could not parse HEAD commit"));
+       }
+       *head = current_head;
+
+       return 0;
+}
+
+/*
+ * Try to commit without forking 'git commit'. In some cases we need
+ * to run 'git commit' to display an error message
+ *
+ * Returns:
+ *  -1 - error unable to commit
+ *   0 - success
+ *   1 - run 'git commit'
+ */
+static int try_to_commit(struct strbuf *msg, const char *author,
+                        struct replay_opts *opts, unsigned int flags,
+                        struct object_id *oid)
+{
+       struct object_id tree;
+       struct commit *current_head;
+       struct commit_list *parents = NULL;
+       struct commit_extra_header *extra = NULL;
+       struct strbuf err = STRBUF_INIT;
+       struct strbuf commit_msg = STRBUF_INIT;
+       char *amend_author = NULL;
+       const char *hook_commit = NULL;
+       enum commit_msg_cleanup_mode cleanup;
+       int res = 0;
+
+       if (parse_head(&current_head))
+               return -1;
+
+       if (flags & AMEND_MSG) {
+               const char *exclude_gpgsig[] = { "gpgsig", NULL };
+               const char *out_enc = get_commit_output_encoding();
+               const char *message = logmsg_reencode(current_head, NULL,
+                                                     out_enc);
+
+               if (!msg) {
+                       const char *orig_message = NULL;
+
+                       find_commit_subject(message, &orig_message);
+                       msg = &commit_msg;
+                       strbuf_addstr(msg, orig_message);
+                       hook_commit = "HEAD";
+               }
+               author = amend_author = get_author(message);
+               unuse_commit_buffer(current_head, message);
+               if (!author) {
+                       res = error(_("unable to parse commit author"));
+                       goto out;
+               }
+               parents = copy_commit_list(current_head->parents);
+               extra = read_commit_extra_headers(current_head, exclude_gpgsig);
+       } else if (current_head) {
+               commit_list_insert(current_head, &parents);
+       }
+
+       if (write_cache_as_tree(&tree, 0, NULL)) {
+               res = error(_("git write-tree failed to write a tree"));
+               goto out;
+       }
+
+       if (!(flags & ALLOW_EMPTY) && !oidcmp(current_head ?
+                                             get_commit_tree_oid(current_head) :
+                                             the_hash_algo->empty_tree, &tree)) {
+               res = 1; /* run 'git commit' to display error message */
+               goto out;
+       }
+
+       if (find_hook("prepare-commit-msg")) {
+               res = run_prepare_commit_msg_hook(msg, hook_commit);
+               if (res)
+                       goto out;
+               if (strbuf_read_file(&commit_msg, git_path_commit_editmsg(),
+                                    2048) < 0) {
+                       res = error_errno(_("unable to read commit message "
+                                             "from '%s'"),
+                                           git_path_commit_editmsg());
+                       goto out;
+               }
+               msg = &commit_msg;
+       }
+
+       cleanup = (flags & CLEANUP_MSG) ? COMMIT_MSG_CLEANUP_ALL :
+                                         opts->default_msg_cleanup;
+
+       if (cleanup != COMMIT_MSG_CLEANUP_NONE)
+               strbuf_stripspace(msg, cleanup == COMMIT_MSG_CLEANUP_ALL);
+       if (!opts->allow_empty_message && message_is_empty(msg, cleanup)) {
+               res = 1; /* run 'git commit' to display error message */
+               goto out;
+       }
+
+       reset_ident_date();
+
+       if (commit_tree_extended(msg->buf, msg->len, &tree, parents,
+                                oid, author, opts->gpg_sign, extra)) {
+               res = error(_("failed to write commit object"));
+               goto out;
+       }
+
+       if (update_head_with_reflog(current_head, oid,
+                                   getenv("GIT_REFLOG_ACTION"), msg, &err)) {
+               res = error("%s", err.buf);
+               goto out;
+       }
+
+       if (flags & AMEND_MSG)
+               commit_post_rewrite(current_head, oid);
+
+out:
+       free_commit_extra_headers(extra);
+       strbuf_release(&err);
+       strbuf_release(&commit_msg);
+       free(amend_author);
+
+       return res;
+}
+
+static int do_commit(const char *msg_file, const char *author,
+                    struct replay_opts *opts, unsigned int flags)
+{
+       int res = 1;
+
+       if (!(flags & EDIT_MSG) && !(flags & VERIFY_MSG) &&
+           !(flags & CREATE_ROOT_COMMIT)) {
+               struct object_id oid;
+               struct strbuf sb = STRBUF_INIT;
+
+               if (msg_file && strbuf_read_file(&sb, msg_file, 2048) < 0)
+                       return error_errno(_("unable to read commit message "
+                                            "from '%s'"),
+                                          msg_file);
+
+               res = try_to_commit(msg_file ? &sb : NULL, author, opts, flags,
+                                   &oid);
+               strbuf_release(&sb);
+               if (!res) {
+                       unlink(git_path_cherry_pick_head(the_repository));
+                       unlink(git_path_merge_msg(the_repository));
+                       if (!is_rebase_i(opts))
+                               print_commit_summary(NULL, &oid,
+                                               SUMMARY_SHOW_AUTHOR_DATE);
+                       return res;
+               }
+       }
+       if (res == 1)
+               return run_git_commit(msg_file, opts, flags);
+
+       return res;
+}
+
 static int is_original_commit_empty(struct commit *commit)
 {
-       const unsigned char *ptree_sha1;
+       const struct object_id *ptree_oid;
 
        if (parse_commit(commit))
-               return error(_("could not parse commit %s\n"),
+               return error(_("could not parse commit %s"),
                             oid_to_hex(&commit->object.oid));
        if (commit->parents) {
                struct commit *parent = commit->parents->item;
                if (parse_commit(parent))
-                       return error(_("could not parse parent commit %s\n"),
+                       return error(_("could not parse parent commit %s"),
                                oid_to_hex(&parent->object.oid));
-               ptree_sha1 = parent->tree->object.oid.hash;
+               ptree_oid = get_commit_tree_oid(parent);
        } else {
-               ptree_sha1 = EMPTY_TREE_SHA1_BIN; /* commit is root */
+               ptree_oid = the_hash_algo->empty_tree; /* commit is root */
        }
 
-       return !hashcmp(ptree_sha1, commit->tree->object.oid.hash);
+       return !oidcmp(ptree_oid, get_commit_tree_oid(commit));
 }
 
 /*
@@ -763,6 +1412,9 @@ enum todo_command {
        TODO_SQUASH,
        /* commands that do something else than handling a single commit */
        TODO_EXEC,
+       TODO_LABEL,
+       TODO_RESET,
+       TODO_MERGE,
        /* commands that do nothing but are counted for reporting progress */
        TODO_NOOP,
        TODO_DROP,
@@ -781,6 +1433,9 @@ static struct {
        { 'f', "fixup" },
        { 's', "squash" },
        { 'x', "exec" },
+       { 'l', "label" },
+       { 't', "reset" },
+       { 'm', "merge" },
        { 0,   "noop" },
        { 'd', "drop" },
        { 0,   NULL }
@@ -793,6 +1448,13 @@ static const char *command_to_string(const enum todo_command command)
        die("Unknown command: %d", command);
 }
 
+static char command_to_char(const enum todo_command command)
+{
+       if (command < TODO_COMMENT && todo_command_info[command].c)
+               return todo_command_info[command].c;
+       return comment_line_char;
+}
+
 static int is_noop(const enum todo_command command)
 {
        return TODO_NOOP <= command;
@@ -803,38 +1465,43 @@ static int is_fixup(enum todo_command command)
        return command == TODO_FIXUP || command == TODO_SQUASH;
 }
 
+/* Does this command create a (non-merge) commit? */
+static int is_pick_or_similar(enum todo_command command)
+{
+       switch (command) {
+       case TODO_PICK:
+       case TODO_REVERT:
+       case TODO_EDIT:
+       case TODO_REWORD:
+       case TODO_FIXUP:
+       case TODO_SQUASH:
+               return 1;
+       default:
+               return 0;
+       }
+}
+
 static int update_squash_messages(enum todo_command command,
                struct commit *commit, struct replay_opts *opts)
 {
        struct strbuf buf = STRBUF_INIT;
-       int count, res;
+       int res;
        const char *message, *body;
 
-       if (file_exists(rebase_path_squash_msg())) {
+       if (opts->current_fixup_count > 0) {
                struct strbuf header = STRBUF_INIT;
-               char *eol, *p;
+               char *eol;
 
-               if (strbuf_read_file(&buf, rebase_path_squash_msg(), 2048) <= 0)
+               if (strbuf_read_file(&buf, rebase_path_squash_msg(), 9) <= 0)
                        return error(_("could not read '%s'"),
                                rebase_path_squash_msg());
 
-               p = buf.buf + 1;
-               eol = strchrnul(buf.buf, '\n');
-               if (buf.buf[0] != comment_line_char ||
-                   (p += strcspn(p, "0123456789\n")) == eol)
-                       return error(_("unexpected 1st line of squash message:"
-                                      "\n\n\t%.*s"),
-                                    (int)(eol - buf.buf), buf.buf);
-               count = strtol(p, NULL, 10);
-
-               if (count < 1)
-                       return error(_("invalid 1st line of squash message:\n"
-                                      "\n\t%.*s"),
-                                    (int)(eol - buf.buf), buf.buf);
+               eol = buf.buf[0] != comment_line_char ?
+                       buf.buf : strchrnul(buf.buf, '\n');
 
                strbuf_addf(&header, "%c ", comment_line_char);
-               strbuf_addf(&header,
-                           _("This is a combination of %d commits."), ++count);
+               strbuf_addf(&header, _("This is a combination of %d commits."),
+                           opts->current_fixup_count + 2);
                strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
                strbuf_release(&header);
        } else {
@@ -857,10 +1524,8 @@ static int update_squash_messages(enum todo_command command,
                                     rebase_path_fixup_msg());
                }
 
-               count = 2;
                strbuf_addf(&buf, "%c ", comment_line_char);
-               strbuf_addf(&buf, _("This is a combination of %d commits."),
-                           count);
+               strbuf_addf(&buf, _("This is a combination of %d commits."), 2);
                strbuf_addf(&buf, "\n%c ", comment_line_char);
                strbuf_addstr(&buf, _("This is the 1st commit message:"));
                strbuf_addstr(&buf, "\n\n");
@@ -877,13 +1542,14 @@ static int update_squash_messages(enum todo_command command,
        if (command == TODO_SQUASH) {
                unlink(rebase_path_fixup_msg());
                strbuf_addf(&buf, "\n%c ", comment_line_char);
-               strbuf_addf(&buf, _("This is the commit message #%d:"), count);
+               strbuf_addf(&buf, _("This is the commit message #%d:"),
+                           ++opts->current_fixup_count);
                strbuf_addstr(&buf, "\n\n");
                strbuf_addstr(&buf, body);
        } else if (command == TODO_FIXUP) {
                strbuf_addf(&buf, "\n%c ", comment_line_char);
                strbuf_addf(&buf, _("The commit message #%d will be skipped:"),
-                           count);
+                           ++opts->current_fixup_count);
                strbuf_addstr(&buf, "\n\n");
                strbuf_add_commented_lines(&buf, body, strlen(body));
        } else
@@ -892,23 +1558,34 @@ static int update_squash_messages(enum todo_command command,
 
        res = write_message(buf.buf, buf.len, rebase_path_squash_msg(), 0);
        strbuf_release(&buf);
+
+       if (!res) {
+               strbuf_addf(&opts->current_fixups, "%s%s %s",
+                           opts->current_fixups.len ? "\n" : "",
+                           command_to_string(command),
+                           oid_to_hex(&commit->object.oid));
+               res = write_message(opts->current_fixups.buf,
+                                   opts->current_fixups.len,
+                                   rebase_path_current_fixups(), 0);
+       }
+
        return res;
 }
 
 static void flush_rewritten_pending(void) {
        struct strbuf buf = STRBUF_INIT;
-       unsigned char newsha1[20];
+       struct object_id newoid;
        FILE *out;
 
-       if (strbuf_read_file(&buf, rebase_path_rewritten_pending(), 82) > 0 &&
-           !get_sha1("HEAD", newsha1) &&
+       if (strbuf_read_file(&buf, rebase_path_rewritten_pending(), (GIT_MAX_HEXSZ + 1) * 2) > 0 &&
+           !get_oid("HEAD", &newoid) &&
            (out = fopen_or_warn(rebase_path_rewritten_list(), "a"))) {
                char *bol = buf.buf, *eol;
 
                while (*bol) {
                        eol = strchrnul(bol, '\n');
                        fprintf(out, "%.*s %s\n", (int)(eol - bol),
-                                       bol, sha1_to_hex(newsha1));
+                                       bol, oid_to_hex(&newoid));
                        if (!*eol)
                                break;
                        bol = eol + 1;
@@ -937,10 +1614,11 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                struct replay_opts *opts, int final_fixup)
 {
        unsigned int flags = opts->edit ? EDIT_MSG : 0;
-       const char *msg_file = opts->edit ? NULL : git_path_merge_msg();
+       const char *msg_file = opts->edit ? NULL : git_path_merge_msg(the_repository);
        struct object_id head;
        struct commit *base, *next, *parent;
        const char *base_label, *next_label;
+       char *author = NULL;
        struct commit_message msg = { NULL, NULL, NULL, NULL };
        struct strbuf msgbuf = STRBUF_INIT;
        int res, unborn = 0, allow;
@@ -952,13 +1630,21 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                 * that represents the "current" state for merge-recursive
                 * to work on.
                 */
-               if (write_cache_as_tree(head.hash, 0, NULL))
+               if (write_cache_as_tree(&head, 0, NULL))
                        return error(_("your index file is unmerged."));
        } else {
                unborn = get_oid("HEAD", &head);
-               if (unborn)
-                       oidcpy(&head, &empty_tree_oid);
-               if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD", 0, 0))
+               /* Do we want to generate a root commit? */
+               if (is_pick_or_similar(command) && opts->have_squash_onto &&
+                   !oidcmp(&head, &opts->squash_onto)) {
+                       if (is_fixup(command))
+                               return error(_("cannot fixup root commit"));
+                       flags |= CREATE_ROOT_COMMIT;
+                       unborn = 1;
+               } else if (unborn)
+                       oidcpy(&head, the_hash_algo->empty_tree);
+               if (index_differs_from(unborn ? empty_tree_oid_hex() : "HEAD",
+                                      NULL, 0))
                        return error_dirty_index(opts);
        }
        discard_cache();
@@ -1001,9 +1687,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        opts);
                if (res || command != TODO_REWORD)
                        goto leave;
-               flags |= EDIT_MSG | AMEND_MSG;
-               if (command == TODO_REWORD)
-                       flags |= VERIFY_MSG;
+               flags |= EDIT_MSG | AMEND_MSG | VERIFY_MSG;
                msg_file = NULL;
                goto fast_forward_edit;
        }
@@ -1056,6 +1740,8 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
                        strbuf_addstr(&msgbuf, ")\n");
                }
+               if (!is_fixup(command))
+                       author = get_author(msg.message);
        }
 
        if (command == TODO_REWORD)
@@ -1070,32 +1756,36 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        flags |= CLEANUP_MSG;
                        msg_file = rebase_path_fixup_msg();
                } else {
-                       const char *dest = git_path_squash_msg();
+                       const char *dest = git_path_squash_msg(the_repository);
                        unlink(dest);
                        if (copy_file(dest, rebase_path_squash_msg(), 0666))
                                return error(_("could not rename '%s' to '%s'"),
                                             rebase_path_squash_msg(), dest);
-                       unlink(git_path_merge_msg());
+                       unlink(git_path_merge_msg(the_repository));
                        msg_file = dest;
                        flags |= EDIT_MSG;
                }
        }
 
+       if (opts->signoff && !is_fixup(command))
+               append_signoff(&msgbuf, 0, 0);
+
        if (is_rebase_i(opts) && write_author_script(msg.message) < 0)
                res = -1;
        else if (!opts->strategy || !strcmp(opts->strategy, "recursive") || command == TODO_REVERT) {
                res = do_recursive_merge(base, next, base_label, next_label,
                                         &head, &msgbuf, opts);
                if (res < 0)
-                       return res;
+                       goto leave;
+
                res |= write_message(msgbuf.buf, msgbuf.len,
-                                    git_path_merge_msg(), 0);
+                                    git_path_merge_msg(the_repository), 0);
        } else {
                struct commit_list *common = NULL;
                struct commit_list *remotes = NULL;
 
                res = write_message(msgbuf.buf, msgbuf.len,
-                                   git_path_merge_msg(), 0);
+                                   git_path_merge_msg(the_repository), 0);
 
                commit_list_insert(base, &common);
                commit_list_insert(next, &remotes);
@@ -1114,12 +1804,12 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
         * write it at all.
         */
        if (command == TODO_PICK && !opts->no_commit && (res == 0 || res == 1) &&
-           update_ref(NULL, "CHERRY_PICK_HEAD", commit->object.oid.hash, NULL,
-                      REF_NODEREF, UPDATE_REFS_MSG_ON_ERR))
+           update_ref(NULL, "CHERRY_PICK_HEAD", &commit->object.oid, NULL,
+                      REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
                res = -1;
        if (command == TODO_REVERT && ((opts->no_commit && res == 0) || res == 1) &&
-           update_ref(NULL, "REVERT_HEAD", commit->object.oid.hash, NULL,
-                      REF_NODEREF, UPDATE_REFS_MSG_ON_ERR))
+           update_ref(NULL, "REVERT_HEAD", &commit->object.oid, NULL,
+                      REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
                res = -1;
 
        if (res) {
@@ -1138,17 +1828,25 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                goto leave;
        } else if (allow)
                flags |= ALLOW_EMPTY;
-       if (!opts->no_commit)
+       if (!opts->no_commit) {
 fast_forward_edit:
-               res = run_git_commit(msg_file, opts, flags);
+               if (author || command == TODO_REVERT || (flags & AMEND_MSG))
+                       res = do_commit(msg_file, author, opts, flags);
+               else
+                       res = error(_("unable to parse commit author"));
+       }
 
        if (!res && final_fixup) {
                unlink(rebase_path_fixup_msg());
                unlink(rebase_path_squash_msg());
+               unlink(rebase_path_current_fixups());
+               strbuf_reset(&opts->current_fixups);
+               opts->current_fixup_count = 0;
        }
 
 leave:
        free_message(commit, &msg);
+       free(author);
        update_abort_safety_file();
 
        return res;
@@ -1173,7 +1871,7 @@ static int prepare_revs(struct replay_opts *opts)
 
 static int read_and_refresh_cache(struct replay_opts *opts)
 {
-       static struct lock_file index_lock;
+       struct lock_file index_lock = LOCK_INIT;
        int index_fd = hold_locked_index(&index_lock, 0);
        if (read_index_preload(&the_index, NULL) < 0) {
                rollback_lock_file(&index_lock);
@@ -1181,20 +1879,24 @@ static int read_and_refresh_cache(struct replay_opts *opts)
                        _(action_name(opts)));
        }
        refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
-       if (the_index.cache_changed && index_fd >= 0) {
-               if (write_locked_index(&the_index, &index_lock, COMMIT_LOCK)) {
-                       rollback_lock_file(&index_lock);
+       if (index_fd >= 0) {
+               if (write_locked_index(&the_index, &index_lock,
+                                      COMMIT_LOCK | SKIP_IF_UNCHANGED)) {
                        return error(_("git %s: failed to refresh the index"),
                                _(action_name(opts)));
                }
        }
-       rollback_lock_file(&index_lock);
        return 0;
 }
 
+enum todo_item_flags {
+       TODO_EDIT_MERGE_MSG = 1
+};
+
 struct todo_item {
        enum todo_command command;
        struct commit *commit;
+       unsigned int flags;
        const char *arg;
        int arg_len;
        size_t offset_in_buf;
@@ -1229,6 +1931,8 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
        char *end_of_object_name;
        int i, saved, status, padding;
 
+       item->flags = 0;
+
        /* left-trim */
        bol += strspn(bol, " \t");
 
@@ -1252,25 +1956,47 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
        if (i >= TODO_COMMENT)
                return -1;
 
+       /* Eat up extra spaces/ tabs before object name */
+       padding = strspn(bol, " \t");
+       bol += padding;
+
        if (item->command == TODO_NOOP) {
+               if (bol != eol)
+                       return error(_("%s does not accept arguments: '%s'"),
+                                    command_to_string(item->command), bol);
                item->commit = NULL;
                item->arg = bol;
                item->arg_len = eol - bol;
                return 0;
        }
 
-       /* Eat up extra spaces/ tabs before object name */
-       padding = strspn(bol, " \t");
        if (!padding)
-               return -1;
-       bol += padding;
+               return error(_("missing arguments for %s"),
+                            command_to_string(item->command));
 
-       if (item->command == TODO_EXEC) {
+       if (item->command == TODO_EXEC || item->command == TODO_LABEL ||
+           item->command == TODO_RESET) {
+               item->commit = NULL;
                item->arg = bol;
                item->arg_len = (int)(eol - bol);
                return 0;
        }
 
+       if (item->command == TODO_MERGE) {
+               if (skip_prefix(bol, "-C", &bol))
+                       bol += strspn(bol, " \t");
+               else if (skip_prefix(bol, "-c", &bol)) {
+                       bol += strspn(bol, " \t");
+                       item->flags |= TODO_EDIT_MERGE_MSG;
+               } else {
+                       item->flags |= TODO_EDIT_MERGE_MSG;
+                       item->commit = NULL;
+                       item->arg = bol;
+                       item->arg_len = (int)(eol - bol);
+                       return 0;
+               }
+       }
+
        end_of_object_name = (char *) bol + strcspn(bol, " \t\n");
        saved = *end_of_object_name;
        *end_of_object_name = '\0';
@@ -1332,22 +2058,48 @@ static int count_commands(struct todo_list *todo_list)
        return count;
 }
 
+static int get_item_line_offset(struct todo_list *todo_list, int index)
+{
+       return index < todo_list->nr ?
+               todo_list->items[index].offset_in_buf : todo_list->buf.len;
+}
+
+static const char *get_item_line(struct todo_list *todo_list, int index)
+{
+       return todo_list->buf.buf + get_item_line_offset(todo_list, index);
+}
+
+static int get_item_line_length(struct todo_list *todo_list, int index)
+{
+       return get_item_line_offset(todo_list, index + 1)
+               -  get_item_line_offset(todo_list, index);
+}
+
+static ssize_t strbuf_read_file_or_whine(struct strbuf *sb, const char *path)
+{
+       int fd;
+       ssize_t len;
+
+       fd = open(path, O_RDONLY);
+       if (fd < 0)
+               return error_errno(_("could not open '%s'"), path);
+       len = strbuf_read(sb, fd, 0);
+       close(fd);
+       if (len < 0)
+               return error(_("could not read '%s'."), path);
+       return len;
+}
+
 static int read_populate_todo(struct todo_list *todo_list,
                        struct replay_opts *opts)
 {
        struct stat st;
        const char *todo_file = get_todo_path(opts);
-       int fd, res;
+       int res;
 
        strbuf_reset(&todo_list->buf);
-       fd = open(todo_file, O_RDONLY);
-       if (fd < 0)
-               return error_errno(_("could not open '%s'"), todo_file);
-       if (strbuf_read(&todo_list->buf, fd, 0) < 0) {
-               close(fd);
-               return error(_("could not read '%s'."), todo_file);
-       }
-       close(fd);
+       if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
+               return -1;
 
        res = stat(todo_file, &st);
        if (res)
@@ -1455,6 +2207,7 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
 {
        int i;
+       char *strategy_opts_string;
 
        strbuf_reset(buf);
        if (!read_oneliner(buf, rebase_path_strategy(), 0))
@@ -1463,7 +2216,11 @@ static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
        if (!read_oneliner(buf, rebase_path_strategy_opts(), 0))
                return;
 
-       opts->xopts_nr = split_cmdline(buf->buf, (const char ***)&opts->xopts);
+       strategy_opts_string = buf->buf;
+       if (*strategy_opts_string == ' ')
+               strategy_opts_string++;
+       opts->xopts_nr = split_cmdline(strategy_opts_string,
+                                      (const char ***)&opts->xopts);
        for (i = 0; i < opts->xopts_nr; i++) {
                const char *arg = opts->xopts[i];
 
@@ -1498,9 +2255,30 @@ static int read_populate_opts(struct replay_opts *opts)
                if (file_exists(rebase_path_verbose()))
                        opts->verbose = 1;
 
+               if (file_exists(rebase_path_signoff())) {
+                       opts->allow_ff = 0;
+                       opts->signoff = 1;
+               }
+
                read_strategy_opts(opts, &buf);
                strbuf_release(&buf);
 
+               if (read_oneliner(&opts->current_fixups,
+                                 rebase_path_current_fixups(), 1)) {
+                       const char *p = opts->current_fixups.buf;
+                       opts->current_fixup_count = 1;
+                       while ((p = strchr(p, '\n'))) {
+                               opts->current_fixup_count++;
+                               p++;
+                       }
+               }
+
+               if (read_oneliner(&buf, rebase_path_squash_onto(), 0)) {
+                       if (get_oid_hex(buf.buf, &opts->squash_onto) < 0)
+                               return error(_("unusable squash-onto"));
+                       opts->have_squash_onto = 1;
+               }
+
                return 0;
        }
 
@@ -1562,25 +2340,24 @@ static int create_seq_dir(void)
 
 static int save_head(const char *head)
 {
-       static struct lock_file head_lock;
+       struct lock_file head_lock = LOCK_INIT;
        struct strbuf buf = STRBUF_INIT;
        int fd;
+       ssize_t written;
 
        fd = hold_lock_file_for_update(&head_lock, git_path_head_file(), 0);
-       if (fd < 0) {
-               rollback_lock_file(&head_lock);
+       if (fd < 0)
                return error_errno(_("could not lock HEAD"));
-       }
        strbuf_addf(&buf, "%s\n", head);
-       if (write_in_full(fd, buf.buf, buf.len) < 0) {
-               rollback_lock_file(&head_lock);
-               return error_errno(_("could not write to '%s'"),
-                                  git_path_head_file());
-       }
-       if (commit_lock_file(&head_lock) < 0) {
+       written = write_in_full(fd, buf.buf, buf.len);
+       strbuf_release(&buf);
+       if (written < 0) {
+               error_errno(_("could not write to '%s'"), git_path_head_file());
                rollback_lock_file(&head_lock);
-               return error(_("failed to finalize '%s'."), git_path_head_file());
+               return -1;
        }
+       if (commit_lock_file(&head_lock) < 0)
+               return error(_("failed to finalize '%s'"), git_path_head_file());
        return 0;
 }
 
@@ -1608,36 +2385,37 @@ static int rollback_is_safe(void)
        return !oidcmp(&actual_head, &expected_head);
 }
 
-static int reset_for_rollback(const unsigned char *sha1)
+static int reset_for_rollback(const struct object_id *oid)
 {
        const char *argv[4];    /* reset --merge <arg> + NULL */
 
        argv[0] = "reset";
        argv[1] = "--merge";
-       argv[2] = sha1_to_hex(sha1);
+       argv[2] = oid_to_hex(oid);
        argv[3] = NULL;
        return run_command_v_opt(argv, RUN_GIT_CMD);
 }
 
 static int rollback_single_pick(void)
 {
-       unsigned char head_sha1[20];
+       struct object_id head_oid;
 
-       if (!file_exists(git_path_cherry_pick_head()) &&
-           !file_exists(git_path_revert_head()))
+       if (!file_exists(git_path_cherry_pick_head(the_repository)) &&
+           !file_exists(git_path_revert_head(the_repository)))
                return error(_("no cherry-pick or revert in progress"));
-       if (read_ref_full("HEAD", 0, head_sha1, NULL))
+       if (read_ref_full("HEAD", 0, &head_oid, NULL))
                return error(_("cannot resolve HEAD"));
-       if (is_null_sha1(head_sha1))
+       if (is_null_oid(&head_oid))
                return error(_("cannot abort from a branch yet to be born"));
-       return reset_for_rollback(head_sha1);
+       return reset_for_rollback(&head_oid);
 }
 
 int sequencer_rollback(struct replay_opts *opts)
 {
        FILE *f;
-       unsigned char sha1[20];
+       struct object_id oid;
        struct strbuf buf = STRBUF_INIT;
+       const char *p;
 
        f = fopen(git_path_head_file(), "r");
        if (!f && errno == ENOENT) {
@@ -1657,12 +2435,12 @@ int sequencer_rollback(struct replay_opts *opts)
                goto fail;
        }
        fclose(f);
-       if (get_sha1_hex(buf.buf, sha1) || buf.buf[40] != '\0') {
+       if (parse_oid_hex(buf.buf, &oid, &p) || *p != '\0') {
                error(_("stored pre-cherry-pick HEAD file '%s' is corrupt"),
                        git_path_head_file());
                goto fail;
        }
-       if (is_null_sha1(sha1)) {
+       if (is_null_oid(&oid)) {
                error(_("cannot abort from a branch yet to be born"));
                goto fail;
        }
@@ -1672,7 +2450,7 @@ int sequencer_rollback(struct replay_opts *opts)
                warning(_("You seem to have moved HEAD. "
                          "Not rewinding, check your HEAD!"));
        } else
-       if (reset_for_rollback(sha1))
+       if (reset_for_rollback(&oid))
                goto fail;
        strbuf_release(&buf);
        return sequencer_remove_state(opts);
@@ -1683,7 +2461,7 @@ int sequencer_rollback(struct replay_opts *opts)
 
 static int save_todo(struct todo_list *todo_list, struct replay_opts *opts)
 {
-       static struct lock_file todo_lock;
+       struct lock_file todo_lock = LOCK_INIT;
        const char *todo_path = get_todo_path(opts);
        int next = todo_list->current, offset, fd;
 
@@ -1697,29 +2475,27 @@ static int save_todo(struct todo_list *todo_list, struct replay_opts *opts)
        fd = hold_lock_file_for_update(&todo_lock, todo_path, 0);
        if (fd < 0)
                return error_errno(_("could not lock '%s'"), todo_path);
-       offset = next < todo_list->nr ?
-               todo_list->items[next].offset_in_buf : todo_list->buf.len;
+       offset = get_item_line_offset(todo_list, next);
        if (write_in_full(fd, todo_list->buf.buf + offset,
                        todo_list->buf.len - offset) < 0)
                return error_errno(_("could not write to '%s'"), todo_path);
        if (commit_lock_file(&todo_lock) < 0)
-               return error(_("failed to finalize '%s'."), todo_path);
+               return error(_("failed to finalize '%s'"), todo_path);
 
-       if (is_rebase_i(opts)) {
-               const char *done_path = rebase_path_done();
-               int fd = open(done_path, O_CREAT | O_WRONLY | O_APPEND, 0666);
-               int prev_offset = !next ? 0 :
-                       todo_list->items[next - 1].offset_in_buf;
+       if (is_rebase_i(opts) && next > 0) {
+               const char *done = rebase_path_done();
+               int fd = open(done, O_CREAT | O_WRONLY | O_APPEND, 0666);
+               int ret = 0;
 
-               if (fd >= 0 && offset > prev_offset &&
-                   write_in_full(fd, todo_list->buf.buf + prev_offset,
-                                 offset - prev_offset) < 0) {
-                       close(fd);
-                       return error_errno(_("could not write to '%s'"),
-                                          done_path);
-               }
-               if (fd >= 0)
-                       close(fd);
+               if (fd < 0)
+                       return 0;
+               if (write_in_full(fd, get_item_line(todo_list, next - 1),
+                                 get_item_line_length(todo_list, next - 1))
+                   < 0)
+                       ret = error_errno(_("could not write to '%s'"), done);
+               if (close(fd) < 0)
+                       ret = error_errno(_("failed to finalize '%s'"), done);
+               return ret;
        }
        return 0;
 }
@@ -1773,6 +2549,9 @@ static int make_patch(struct commit *commit, struct replay_opts *opts)
        p = short_commit_name(commit);
        if (write_message(p, strlen(p), rebase_path_stopped_sha(), 1) < 0)
                return -1;
+       if (update_ref("rebase", "REBASE_HEAD", &commit->object.oid,
+                      NULL, REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
+               res |= error(_("could not update %s"), "REBASE_HEAD");
 
        strbuf_addf(&buf, "%s/patch", get_dir(opts));
        memset(&log_tree_opt, 0, sizeof(log_tree_opt));
@@ -1806,13 +2585,13 @@ static int make_patch(struct commit *commit, struct replay_opts *opts)
 
 static int intend_to_amend(void)
 {
-       unsigned char head[20];
+       struct object_id head;
        char *p;
 
-       if (get_sha1("HEAD", head))
+       if (get_oid("HEAD", &head))
                return error(_("cannot read HEAD"));
 
-       p = sha1_to_hex(head);
+       p = oid_to_hex(&head);
        return write_message(p, strlen(p), rebase_path_amend(), 1);
 }
 
@@ -1844,25 +2623,28 @@ static int error_with_patch(struct commit *commit,
 static int error_failed_squash(struct commit *commit,
        struct replay_opts *opts, int subject_len, const char *subject)
 {
-       if (rename(rebase_path_squash_msg(), rebase_path_message()))
-               return error(_("could not rename '%s' to '%s'"),
+       if (copy_file(rebase_path_message(), rebase_path_squash_msg(), 0666))
+               return error(_("could not copy '%s' to '%s'"),
                        rebase_path_squash_msg(), rebase_path_message());
-       unlink(rebase_path_fixup_msg());
-       unlink(git_path_merge_msg());
-       if (copy_file(git_path_merge_msg(), rebase_path_message(), 0666))
+       unlink(git_path_merge_msg(the_repository));
+       if (copy_file(git_path_merge_msg(the_repository), rebase_path_message(), 0666))
                return error(_("could not copy '%s' to '%s'"),
-                            rebase_path_message(), git_path_merge_msg());
+                            rebase_path_message(),
+                            git_path_merge_msg(the_repository));
        return error_with_patch(commit, subject, subject_len, opts, 1, 0);
 }
 
 static int do_exec(const char *command_line)
 {
+       struct argv_array child_env = ARGV_ARRAY_INIT;
        const char *child_argv[] = { NULL, NULL };
        int dirty, status;
 
        fprintf(stderr, "Executing: %s\n", command_line);
        child_argv[0] = command_line;
-       status = run_command_v_opt(child_argv, RUN_USING_SHELL);
+       argv_array_pushf(&child_env, "GIT_DIR=%s", absolute_path(get_git_dir()));
+       status = run_command_v_opt_cd_env(child_argv, RUN_USING_SHELL, NULL,
+                                         child_env.argv);
 
        /* force re-reading of the cache */
        if (discard_cache() < 0 || read_cache() < 0)
@@ -1892,9 +2674,382 @@ static int do_exec(const char *command_line)
                status = 1;
        }
 
+       argv_array_clear(&child_env);
+
        return status;
 }
 
+static int safe_append(const char *filename, const char *fmt, ...)
+{
+       va_list ap;
+       struct lock_file lock = LOCK_INIT;
+       int fd = hold_lock_file_for_update(&lock, filename,
+                                          LOCK_REPORT_ON_ERROR);
+       struct strbuf buf = STRBUF_INIT;
+
+       if (fd < 0)
+               return -1;
+
+       if (strbuf_read_file(&buf, filename, 0) < 0 && errno != ENOENT) {
+               error_errno(_("could not read '%s'"), filename);
+               rollback_lock_file(&lock);
+               return -1;
+       }
+       strbuf_complete(&buf, '\n');
+       va_start(ap, fmt);
+       strbuf_vaddf(&buf, fmt, ap);
+       va_end(ap);
+
+       if (write_in_full(fd, buf.buf, buf.len) < 0) {
+               error_errno(_("could not write to '%s'"), filename);
+               strbuf_release(&buf);
+               rollback_lock_file(&lock);
+               return -1;
+       }
+       if (commit_lock_file(&lock) < 0) {
+               strbuf_release(&buf);
+               rollback_lock_file(&lock);
+               return error(_("failed to finalize '%s'"), filename);
+       }
+
+       strbuf_release(&buf);
+       return 0;
+}
+
+static int do_label(const char *name, int len)
+{
+       struct ref_store *refs = get_main_ref_store(the_repository);
+       struct ref_transaction *transaction;
+       struct strbuf ref_name = STRBUF_INIT, err = STRBUF_INIT;
+       struct strbuf msg = STRBUF_INIT;
+       int ret = 0;
+       struct object_id head_oid;
+
+       if (len == 1 && *name == '#')
+               return error("Illegal label name: '%.*s'", len, name);
+
+       strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
+       strbuf_addf(&msg, "rebase -i (label) '%.*s'", len, name);
+
+       transaction = ref_store_transaction_begin(refs, &err);
+       if (!transaction) {
+               error("%s", err.buf);
+               ret = -1;
+       } else if (get_oid("HEAD", &head_oid)) {
+               error(_("could not read HEAD"));
+               ret = -1;
+       } else if (ref_transaction_update(transaction, ref_name.buf, &head_oid,
+                                         NULL, 0, msg.buf, &err) < 0 ||
+                  ref_transaction_commit(transaction, &err)) {
+               error("%s", err.buf);
+               ret = -1;
+       }
+       ref_transaction_free(transaction);
+       strbuf_release(&err);
+       strbuf_release(&msg);
+
+       if (!ret)
+               ret = safe_append(rebase_path_refs_to_delete(),
+                                 "%s\n", ref_name.buf);
+       strbuf_release(&ref_name);
+
+       return ret;
+}
+
+static const char *reflog_message(struct replay_opts *opts,
+       const char *sub_action, const char *fmt, ...);
+
+static int do_reset(const char *name, int len, struct replay_opts *opts)
+{
+       struct strbuf ref_name = STRBUF_INIT;
+       struct object_id oid;
+       struct lock_file lock = LOCK_INIT;
+       struct tree_desc desc;
+       struct tree *tree;
+       struct unpack_trees_options unpack_tree_opts;
+       int ret = 0, i;
+
+       if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
+               return -1;
+
+       if (len == 10 && !strncmp("[new root]", name, len)) {
+               if (!opts->have_squash_onto) {
+                       const char *hex;
+                       if (commit_tree("", 0, the_hash_algo->empty_tree,
+                                       NULL, &opts->squash_onto,
+                                       NULL, NULL))
+                               return error(_("writing fake root commit"));
+                       opts->have_squash_onto = 1;
+                       hex = oid_to_hex(&opts->squash_onto);
+                       if (write_message(hex, strlen(hex),
+                                         rebase_path_squash_onto(), 0))
+                               return error(_("writing squash-onto"));
+               }
+               oidcpy(&oid, &opts->squash_onto);
+       } else {
+               /* Determine the length of the label */
+               for (i = 0; i < len; i++)
+                       if (isspace(name[i]))
+                               len = i;
+
+               strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
+               if (get_oid(ref_name.buf, &oid) &&
+                   get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
+                       error(_("could not read '%s'"), ref_name.buf);
+                       rollback_lock_file(&lock);
+                       strbuf_release(&ref_name);
+                       return -1;
+               }
+       }
+
+       memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
+       setup_unpack_trees_porcelain(&unpack_tree_opts, "reset");
+       unpack_tree_opts.head_idx = 1;
+       unpack_tree_opts.src_index = &the_index;
+       unpack_tree_opts.dst_index = &the_index;
+       unpack_tree_opts.fn = oneway_merge;
+       unpack_tree_opts.merge = 1;
+       unpack_tree_opts.update = 1;
+
+       if (read_cache_unmerged()) {
+               rollback_lock_file(&lock);
+               strbuf_release(&ref_name);
+               return error_resolve_conflict(_(action_name(opts)));
+       }
+
+       if (!fill_tree_descriptor(&desc, &oid)) {
+               error(_("failed to find tree of %s"), oid_to_hex(&oid));
+               rollback_lock_file(&lock);
+               free((void *)desc.buffer);
+               strbuf_release(&ref_name);
+               return -1;
+       }
+
+       if (unpack_trees(1, &desc, &unpack_tree_opts)) {
+               rollback_lock_file(&lock);
+               free((void *)desc.buffer);
+               strbuf_release(&ref_name);
+               return -1;
+       }
+
+       tree = parse_tree_indirect(&oid);
+       prime_cache_tree(&the_index, tree);
+
+       if (write_locked_index(&the_index, &lock, COMMIT_LOCK) < 0)
+               ret = error(_("could not write index"));
+       free((void *)desc.buffer);
+
+       if (!ret)
+               ret = update_ref(reflog_message(opts, "reset", "'%.*s'",
+                                               len, name), "HEAD", &oid,
+                                NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+
+       strbuf_release(&ref_name);
+       return ret;
+}
+
+static int do_merge(struct commit *commit, const char *arg, int arg_len,
+                   int flags, struct replay_opts *opts)
+{
+       int run_commit_flags = (flags & TODO_EDIT_MERGE_MSG) ?
+               EDIT_MSG | VERIFY_MSG : 0;
+       struct strbuf ref_name = STRBUF_INIT;
+       struct commit *head_commit, *merge_commit, *i;
+       struct commit_list *bases, *j, *reversed = NULL;
+       struct merge_options o;
+       int merge_arg_len, oneline_offset, can_fast_forward, ret;
+       static struct lock_file lock;
+       const char *p;
+
+       if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0) {
+               ret = -1;
+               goto leave_merge;
+       }
+
+       head_commit = lookup_commit_reference_by_name("HEAD");
+       if (!head_commit) {
+               ret = error(_("cannot merge without a current revision"));
+               goto leave_merge;
+       }
+
+       oneline_offset = arg_len;
+       merge_arg_len = strcspn(arg, " \t\n");
+       p = arg + merge_arg_len;
+       p += strspn(p, " \t\n");
+       if (*p == '#' && (!p[1] || isspace(p[1]))) {
+               p += 1 + strspn(p + 1, " \t\n");
+               oneline_offset = p - arg;
+       } else if (p - arg < arg_len)
+               BUG("octopus merges are not supported yet: '%s'", p);
+
+       strbuf_addf(&ref_name, "refs/rewritten/%.*s", merge_arg_len, arg);
+       merge_commit = lookup_commit_reference_by_name(ref_name.buf);
+       if (!merge_commit) {
+               /* fall back to non-rewritten ref or commit */
+               strbuf_splice(&ref_name, 0, strlen("refs/rewritten/"), "", 0);
+               merge_commit = lookup_commit_reference_by_name(ref_name.buf);
+       }
+
+       if (!merge_commit) {
+               ret = error(_("could not resolve '%s'"), ref_name.buf);
+               goto leave_merge;
+       }
+
+       if (opts->have_squash_onto &&
+           !oidcmp(&head_commit->object.oid, &opts->squash_onto)) {
+               /*
+                * When the user tells us to "merge" something into a
+                * "[new root]", let's simply fast-forward to the merge head.
+                */
+               rollback_lock_file(&lock);
+               ret = fast_forward_to(&merge_commit->object.oid,
+                                      &head_commit->object.oid, 0, opts);
+               goto leave_merge;
+       }
+
+       if (commit) {
+               const char *message = get_commit_buffer(commit, NULL);
+               const char *body;
+               int len;
+
+               if (!message) {
+                       ret = error(_("could not get commit message of '%s'"),
+                                   oid_to_hex(&commit->object.oid));
+                       goto leave_merge;
+               }
+               write_author_script(message);
+               find_commit_subject(message, &body);
+               len = strlen(body);
+               ret = write_message(body, len, git_path_merge_msg(the_repository), 0);
+               unuse_commit_buffer(commit, message);
+               if (ret) {
+                       error_errno(_("could not write '%s'"),
+                                   git_path_merge_msg(the_repository));
+                       goto leave_merge;
+               }
+       } else {
+               struct strbuf buf = STRBUF_INIT;
+               int len;
+
+               strbuf_addf(&buf, "author %s", git_author_info(0));
+               write_author_script(buf.buf);
+               strbuf_reset(&buf);
+
+               if (oneline_offset < arg_len) {
+                       p = arg + oneline_offset;
+                       len = arg_len - oneline_offset;
+               } else {
+                       strbuf_addf(&buf, "Merge branch '%.*s'",
+                                   merge_arg_len, arg);
+                       p = buf.buf;
+                       len = buf.len;
+               }
+
+               ret = write_message(p, len, git_path_merge_msg(the_repository), 0);
+               strbuf_release(&buf);
+               if (ret) {
+                       error_errno(_("could not write '%s'"),
+                                   git_path_merge_msg(the_repository));
+                       goto leave_merge;
+               }
+       }
+
+       /*
+        * If HEAD is not identical to the first parent of the original merge
+        * commit, we cannot fast-forward.
+        */
+       can_fast_forward = opts->allow_ff && commit && commit->parents &&
+               !oidcmp(&commit->parents->item->object.oid,
+                       &head_commit->object.oid);
+
+       /*
+        * If the merge head is different from the original one, we cannot
+        * fast-forward.
+        */
+       if (can_fast_forward) {
+               struct commit_list *second_parent = commit->parents->next;
+
+               if (second_parent && !second_parent->next &&
+                   oidcmp(&merge_commit->object.oid,
+                          &second_parent->item->object.oid))
+                       can_fast_forward = 0;
+       }
+
+       if (can_fast_forward && commit->parents->next &&
+           !commit->parents->next->next &&
+           !oidcmp(&commit->parents->next->item->object.oid,
+                   &merge_commit->object.oid)) {
+               rollback_lock_file(&lock);
+               ret = fast_forward_to(&commit->object.oid,
+                                     &head_commit->object.oid, 0, opts);
+               goto leave_merge;
+       }
+
+       write_message(oid_to_hex(&merge_commit->object.oid), GIT_SHA1_HEXSZ,
+                     git_path_merge_head(the_repository), 0);
+       write_message("no-ff", 5, git_path_merge_mode(the_repository), 0);
+
+       bases = get_merge_bases(head_commit, merge_commit);
+       if (bases && !oidcmp(&merge_commit->object.oid,
+                            &bases->item->object.oid)) {
+               ret = 0;
+               /* skip merging an ancestor of HEAD */
+               goto leave_merge;
+       }
+
+       for (j = bases; j; j = j->next)
+               commit_list_insert(j->item, &reversed);
+       free_commit_list(bases);
+
+       read_cache();
+       init_merge_options(&o);
+       o.branch1 = "HEAD";
+       o.branch2 = ref_name.buf;
+       o.buffer_output = 2;
+
+       ret = merge_recursive(&o, head_commit, merge_commit, reversed, &i);
+       if (ret <= 0)
+               fputs(o.obuf.buf, stdout);
+       strbuf_release(&o.obuf);
+       if (ret < 0) {
+               error(_("could not even attempt to merge '%.*s'"),
+                     merge_arg_len, arg);
+               goto leave_merge;
+       }
+       /*
+        * The return value of merge_recursive() is 1 on clean, and 0 on
+        * unclean merge.
+        *
+        * Let's reverse that, so that do_merge() returns 0 upon success and
+        * 1 upon failed merge (keeping the return value -1 for the cases where
+        * we will want to reschedule the `merge` command).
+        */
+       ret = !ret;
+
+       if (active_cache_changed &&
+           write_locked_index(&the_index, &lock, COMMIT_LOCK)) {
+               ret = error(_("merge: Unable to write new index file"));
+               goto leave_merge;
+       }
+
+       rollback_lock_file(&lock);
+       if (ret)
+               rerere(opts->allow_rerere_auto);
+       else
+               /*
+                * In case of problems, we now want to return a positive
+                * value (a negative one would indicate that the `merge`
+                * command needs to be rescheduled).
+                */
+               ret = !!run_git_commit(git_path_merge_msg(the_repository), opts,
+                                    run_commit_flags);
+
+leave_merge:
+       strbuf_release(&ref_name);
+       rollback_lock_file(&lock);
+       return ret;
+}
+
 static int is_final_fixup(struct todo_list *todo_list)
 {
        int i = todo_list->current;
@@ -1985,9 +3140,20 @@ static const char *reflog_message(struct replay_opts *opts,
        return buf.buf;
 }
 
+static const char rescheduled_advice[] =
+N_("Could not execute the todo command\n"
+"\n"
+"    %.*s"
+"\n"
+"It has been rescheduled; To edit the command before continuing, please\n"
+"edit the todo list first:\n"
+"\n"
+"    git rebase --edit-todo\n"
+"    git rebase --continue\n");
+
 static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
 {
-       int res = 0;
+       int res = 0, reschedule = 0;
 
        setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
        if (opts->allow_ff)
@@ -2019,6 +3185,7 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                        unlink(rebase_path_author_script());
                        unlink(rebase_path_stopped_sha());
                        unlink(rebase_path_amend());
+                       delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
                }
                if (item->command <= TODO_SQUASH) {
                        if (is_rebase_i(opts))
@@ -2029,6 +3196,11 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                                        opts, is_final_fixup(todo_list));
                        if (is_rebase_i(opts) && res < 0) {
                                /* Reschedule */
+                               advise(_(rescheduled_advice),
+                                      get_item_line_length(todo_list,
+                                                           todo_list->current),
+                                      get_item_line(todo_list,
+                                                    todo_list->current));
                                todo_list->current--;
                                if (save_todo(todo_list, opts))
                                        return -1;
@@ -2052,10 +3224,27 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                                        intend_to_amend();
                                return error_failed_squash(item->commit, opts,
                                        item->arg_len, item->arg);
-                       } else if (res && is_rebase_i(opts))
+                       } else if (res && is_rebase_i(opts) && item->commit) {
+                               int to_amend = 0;
+                               struct object_id oid;
+
+                               /*
+                                * If we are rewording and have either
+                                * fast-forwarded already, or are about to
+                                * create a new root commit, we want to amend,
+                                * otherwise we do not.
+                                */
+                               if (item->command == TODO_REWORD &&
+                                   !get_oid("HEAD", &oid) &&
+                                   (!oidcmp(&item->commit->object.oid, &oid) ||
+                                    (opts->have_squash_onto &&
+                                     !oidcmp(&opts->squash_onto, &oid))))
+                                       to_amend = 1;
+
                                return res | error_with_patch(item->commit,
-                                       item->arg, item->arg_len, opts, res,
-                                       item->command == TODO_REWORD);
+                                               item->arg, item->arg_len, opts,
+                                               res, to_amend);
+                       }
                } else if (item->command == TODO_EXEC) {
                        char *end_of_arg = (char *)(item->arg + item->arg_len);
                        int saved = *end_of_arg;
@@ -2078,9 +3267,44 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                                /* `current` will be incremented below */
                                todo_list->current = -1;
                        }
+               } else if (item->command == TODO_LABEL) {
+                       if ((res = do_label(item->arg, item->arg_len)))
+                               reschedule = 1;
+               } else if (item->command == TODO_RESET) {
+                       if ((res = do_reset(item->arg, item->arg_len, opts)))
+                               reschedule = 1;
+               } else if (item->command == TODO_MERGE) {
+                       if ((res = do_merge(item->commit,
+                                           item->arg, item->arg_len,
+                                           item->flags, opts)) < 0)
+                               reschedule = 1;
+                       else if (item->commit)
+                               record_in_rewritten(&item->commit->object.oid,
+                                                   peek_command(todo_list, 1));
+                       if (res > 0)
+                               /* failed with merge conflicts */
+                               return error_with_patch(item->commit,
+                                                       item->arg,
+                                                       item->arg_len, opts,
+                                                       res, 0);
                } else if (!is_noop(item->command))
                        return error(_("unknown command %d"), item->command);
 
+               if (reschedule) {
+                       advise(_(rescheduled_advice),
+                              get_item_line_length(todo_list,
+                                                   todo_list->current),
+                              get_item_line(todo_list, todo_list->current));
+                       todo_list->current--;
+                       if (save_todo(todo_list, opts))
+                               return -1;
+                       if (item->commit)
+                               return error_with_patch(item->commit,
+                                                       item->arg,
+                                                       item->arg_len, opts,
+                                                       res, 0);
+               }
+
                todo_list->current++;
                if (res)
                        return res;
@@ -2097,10 +3321,10 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                if (read_oneliner(&head_ref, rebase_path_head_name(), 0) &&
                                starts_with(head_ref.buf, "refs/")) {
                        const char *msg;
-                       unsigned char head[20], orig[20];
+                       struct object_id head, orig;
                        int res;
 
-                       if (get_sha1("HEAD", head)) {
+                       if (get_oid("HEAD", &head)) {
                                res = error(_("cannot read HEAD"));
 cleanup_head_ref:
                                strbuf_release(&head_ref);
@@ -2108,7 +3332,7 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                                return res;
                        }
                        if (!read_oneliner(&buf, rebase_path_orig_head(), 0) ||
-                                       get_sha1_hex(buf.buf, orig)) {
+                                       get_oid_hex(buf.buf, &orig)) {
                                res = error(_("could not read orig-head"));
                                goto cleanup_head_ref;
                        }
@@ -2119,8 +3343,8 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                        }
                        msg = reflog_message(opts, "finish", "%s onto %s",
                                head_ref.buf, buf.buf);
-                       if (update_ref(msg, head_ref.buf, head, orig,
-                                       REF_NODEREF, UPDATE_REFS_MSG_ON_ERR)) {
+                       if (update_ref(msg, head_ref.buf, &head, &orig,
+                                      REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR)) {
                                res = error(_("could not update %s"),
                                        head_ref.buf);
                                goto cleanup_head_ref;
@@ -2147,8 +3371,8 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                        log_tree_opt.disable_stdin = 1;
 
                        if (read_oneliner(&buf, rebase_path_orig_head(), 0) &&
-                           !get_sha1(buf.buf, orig.hash) &&
-                           !get_sha1("HEAD", head.hash)) {
+                           !get_oid(buf.buf, &orig) &&
+                           !get_oid("HEAD", &head)) {
                                diff_tree_oid(&orig, &head, "",
                                              &log_tree_opt.diffopt);
                                log_tree_diff_flush(&log_tree_opt);
@@ -2201,50 +3425,135 @@ static int continue_single_pick(void)
 {
        const char *argv[] = { "commit", NULL };
 
-       if (!file_exists(git_path_cherry_pick_head()) &&
-           !file_exists(git_path_revert_head()))
+       if (!file_exists(git_path_cherry_pick_head(the_repository)) &&
+           !file_exists(git_path_revert_head(the_repository)))
                return error(_("no cherry-pick or revert in progress"));
        return run_command_v_opt(argv, RUN_GIT_CMD);
 }
 
-static int commit_staged_changes(struct replay_opts *opts)
+static int commit_staged_changes(struct replay_opts *opts,
+                                struct todo_list *todo_list)
 {
        unsigned int flags = ALLOW_EMPTY | EDIT_MSG;
+       unsigned int final_fixup = 0, is_clean;
 
        if (has_unstaged_changes(1))
                return error(_("cannot rebase: You have unstaged changes."));
-       if (!has_uncommitted_changes(0)) {
-               const char *cherry_pick_head = git_path_cherry_pick_head();
 
-               if (file_exists(cherry_pick_head) && unlink(cherry_pick_head))
-                       return error(_("could not remove CHERRY_PICK_HEAD"));
-               return 0;
-       }
+       is_clean = !has_uncommitted_changes(0);
 
        if (file_exists(rebase_path_amend())) {
                struct strbuf rev = STRBUF_INIT;
-               unsigned char head[20], to_amend[20];
+               struct object_id head, to_amend;
 
-               if (get_sha1("HEAD", head))
+               if (get_oid("HEAD", &head))
                        return error(_("cannot amend non-existing commit"));
                if (!read_oneliner(&rev, rebase_path_amend(), 0))
                        return error(_("invalid file: '%s'"), rebase_path_amend());
-               if (get_sha1_hex(rev.buf, to_amend))
+               if (get_oid_hex(rev.buf, &to_amend))
                        return error(_("invalid contents: '%s'"),
                                rebase_path_amend());
-               if (hashcmp(head, to_amend))
+               if (!is_clean && oidcmp(&head, &to_amend))
                        return error(_("\nYou have uncommitted changes in your "
                                       "working tree. Please, commit them\n"
                                       "first and then run 'git rebase "
                                       "--continue' again."));
+               /*
+                * When skipping a failed fixup/squash, we need to edit the
+                * commit message, the current fixup list and count, and if it
+                * was the last fixup/squash in the chain, we need to clean up
+                * the commit message and if there was a squash, let the user
+                * edit it.
+                */
+               if (is_clean && !oidcmp(&head, &to_amend) &&
+                   opts->current_fixup_count > 0 &&
+                   file_exists(rebase_path_stopped_sha())) {
+                       const char *p = opts->current_fixups.buf;
+                       int len = opts->current_fixups.len;
+
+                       opts->current_fixup_count--;
+                       if (!len)
+                               BUG("Incorrect current_fixups:\n%s", p);
+                       while (len && p[len - 1] != '\n')
+                               len--;
+                       strbuf_setlen(&opts->current_fixups, len);
+                       if (write_message(p, len, rebase_path_current_fixups(),
+                                         0) < 0)
+                               return error(_("could not write file: '%s'"),
+                                            rebase_path_current_fixups());
+
+                       /*
+                        * If a fixup/squash in a fixup/squash chain failed, the
+                        * commit message is already correct, no need to commit
+                        * it again.
+                        *
+                        * Only if it is the final command in the fixup/squash
+                        * chain, and only if the chain is longer than a single
+                        * fixup/squash command (which was just skipped), do we
+                        * actually need to re-commit with a cleaned up commit
+                        * message.
+                        */
+                       if (opts->current_fixup_count > 0 &&
+                           !is_fixup(peek_command(todo_list, 0))) {
+                               final_fixup = 1;
+                               /*
+                                * If there was not a single "squash" in the
+                                * chain, we only need to clean up the commit
+                                * message, no need to bother the user with
+                                * opening the commit message in the editor.
+                                */
+                               if (!starts_with(p, "squash ") &&
+                                   !strstr(p, "\nsquash "))
+                                       flags = (flags & ~EDIT_MSG) | CLEANUP_MSG;
+                       } else if (is_fixup(peek_command(todo_list, 0))) {
+                               /*
+                                * We need to update the squash message to skip
+                                * the latest commit message.
+                                */
+                               struct commit *commit;
+                               const char *path = rebase_path_squash_msg();
+
+                               if (parse_head(&commit) ||
+                                   !(p = get_commit_buffer(commit, NULL)) ||
+                                   write_message(p, strlen(p), path, 0)) {
+                                       unuse_commit_buffer(commit, p);
+                                       return error(_("could not write file: "
+                                                      "'%s'"), path);
+                               }
+                               unuse_commit_buffer(commit, p);
+                       }
+               }
 
                strbuf_release(&rev);
                flags |= AMEND_MSG;
        }
 
-       if (run_git_commit(rebase_path_message(), opts, flags))
+       if (is_clean) {
+               const char *cherry_pick_head = git_path_cherry_pick_head(the_repository);
+
+               if (file_exists(cherry_pick_head) && unlink(cherry_pick_head))
+                       return error(_("could not remove CHERRY_PICK_HEAD"));
+               if (!final_fixup)
+                       return 0;
+       }
+
+       if (run_git_commit(final_fixup ? NULL : rebase_path_message(),
+                          opts, flags))
                return error(_("could not commit staged changes."));
        unlink(rebase_path_amend());
+       if (final_fixup) {
+               unlink(rebase_path_fixup_msg());
+               unlink(rebase_path_squash_msg());
+       }
+       if (opts->current_fixup_count > 0) {
+               /*
+                * Whether final fixup or not, we just cleaned up the commit
+                * message...
+                */
+               unlink(rebase_path_current_fixups());
+               strbuf_reset(&opts->current_fixups);
+               opts->current_fixup_count = 0;
+       }
        return 0;
 }
 
@@ -2256,25 +3565,27 @@ int sequencer_continue(struct replay_opts *opts)
        if (read_and_refresh_cache(opts))
                return -1;
 
+       if (read_populate_opts(opts))
+               return -1;
        if (is_rebase_i(opts)) {
-               if (commit_staged_changes(opts))
+               if ((res = read_populate_todo(&todo_list, opts)))
+                       goto release_todo_list;
+               if (commit_staged_changes(opts, &todo_list))
                        return -1;
        } else if (!file_exists(get_todo_path(opts)))
                return continue_single_pick();
-       if (read_populate_opts(opts))
-               return -1;
-       if ((res = read_populate_todo(&todo_list, opts)))
+       else if ((res = read_populate_todo(&todo_list, opts)))
                goto release_todo_list;
 
        if (!is_rebase_i(opts)) {
                /* Verify that the conflict has been resolved */
-               if (file_exists(git_path_cherry_pick_head()) ||
-                   file_exists(git_path_revert_head())) {
+               if (file_exists(git_path_cherry_pick_head(the_repository)) ||
+                   file_exists(git_path_revert_head(the_repository))) {
                        res = continue_single_pick();
                        if (res)
                                goto release_todo_list;
                }
-               if (index_differs_from("HEAD", 0, 0)) {
+               if (index_differs_from("HEAD", NULL, 0)) {
                        res = error_dirty_index(opts);
                        goto release_todo_list;
                }
@@ -2284,7 +3595,7 @@ int sequencer_continue(struct replay_opts *opts)
                struct object_id oid;
 
                if (read_oneliner(&buf, rebase_path_stopped_sha(), 1) &&
-                   !get_sha1_committish(buf.buf, oid.hash))
+                   !get_oid_committish(buf.buf, &oid))
                        record_in_rewritten(&oid, peek_command(&todo_list, 0));
                strbuf_release(&buf);
        }
@@ -2322,9 +3633,11 @@ int sequencer_pick_revisions(struct replay_opts *opts)
 
                if (!get_oid(name, &oid)) {
                        if (!lookup_commit_reference_gently(&oid, 1)) {
-                               enum object_type type = sha1_object_info(oid.hash, NULL);
+                               enum object_type type = oid_object_info(the_repository,
+                                                                       &oid,
+                                                                       NULL);
                                return error(_("%s: can't cherry-pick a %s"),
-                                       name, typename(type));
+                                       name, type_name(type));
                        }
                } else
                        return error(_("%s: bad revision"), name);
@@ -2431,3 +3744,895 @@ void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
 
        strbuf_release(&sob);
 }
+
+struct labels_entry {
+       struct hashmap_entry entry;
+       char label[FLEX_ARRAY];
+};
+
+static int labels_cmp(const void *fndata, const struct labels_entry *a,
+                     const struct labels_entry *b, const void *key)
+{
+       return key ? strcmp(a->label, key) : strcmp(a->label, b->label);
+}
+
+struct string_entry {
+       struct oidmap_entry entry;
+       char string[FLEX_ARRAY];
+};
+
+struct label_state {
+       struct oidmap commit2label;
+       struct hashmap labels;
+       struct strbuf buf;
+};
+
+static const char *label_oid(struct object_id *oid, const char *label,
+                            struct label_state *state)
+{
+       struct labels_entry *labels_entry;
+       struct string_entry *string_entry;
+       struct object_id dummy;
+       size_t len;
+       int i;
+
+       string_entry = oidmap_get(&state->commit2label, oid);
+       if (string_entry)
+               return string_entry->string;
+
+       /*
+        * For "uninteresting" commits, i.e. commits that are not to be
+        * rebased, and which can therefore not be labeled, we use a unique
+        * abbreviation of the commit name. This is slightly more complicated
+        * than calling find_unique_abbrev() because we also need to make
+        * sure that the abbreviation does not conflict with any other
+        * label.
+        *
+        * We disallow "interesting" commits to be labeled by a string that
+        * is a valid full-length hash, to ensure that we always can find an
+        * abbreviation for any uninteresting commit's names that does not
+        * clash with any other label.
+        */
+       if (!label) {
+               char *p;
+
+               strbuf_reset(&state->buf);
+               strbuf_grow(&state->buf, GIT_SHA1_HEXSZ);
+               label = p = state->buf.buf;
+
+               find_unique_abbrev_r(p, oid, default_abbrev);
+
+               /*
+                * We may need to extend the abbreviated hash so that there is
+                * no conflicting label.
+                */
+               if (hashmap_get_from_hash(&state->labels, strihash(p), p)) {
+                       size_t i = strlen(p) + 1;
+
+                       oid_to_hex_r(p, oid);
+                       for (; i < GIT_SHA1_HEXSZ; i++) {
+                               char save = p[i];
+                               p[i] = '\0';
+                               if (!hashmap_get_from_hash(&state->labels,
+                                                          strihash(p), p))
+                                       break;
+                               p[i] = save;
+                       }
+               }
+       } else if (((len = strlen(label)) == the_hash_algo->hexsz &&
+                   !get_oid_hex(label, &dummy)) ||
+                  (len == 1 && *label == '#') ||
+                  hashmap_get_from_hash(&state->labels,
+                                        strihash(label), label)) {
+               /*
+                * If the label already exists, or if the label is a valid full
+                * OID, or the label is a '#' (which we use as a separator
+                * between merge heads and oneline), we append a dash and a
+                * number to make it unique.
+                */
+               struct strbuf *buf = &state->buf;
+
+               strbuf_reset(buf);
+               strbuf_add(buf, label, len);
+
+               for (i = 2; ; i++) {
+                       strbuf_setlen(buf, len);
+                       strbuf_addf(buf, "-%d", i);
+                       if (!hashmap_get_from_hash(&state->labels,
+                                                  strihash(buf->buf),
+                                                  buf->buf))
+                               break;
+               }
+
+               label = buf->buf;
+       }
+
+       FLEX_ALLOC_STR(labels_entry, label, label);
+       hashmap_entry_init(labels_entry, strihash(label));
+       hashmap_add(&state->labels, labels_entry);
+
+       FLEX_ALLOC_STR(string_entry, string, label);
+       oidcpy(&string_entry->entry.oid, oid);
+       oidmap_put(&state->commit2label, string_entry);
+
+       return string_entry->string;
+}
+
+static int make_script_with_merges(struct pretty_print_context *pp,
+                                  struct rev_info *revs, FILE *out,
+                                  unsigned flags)
+{
+       int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
+       int rebase_cousins = flags & TODO_LIST_REBASE_COUSINS;
+       struct strbuf buf = STRBUF_INIT, oneline = STRBUF_INIT;
+       struct strbuf label = STRBUF_INIT;
+       struct commit_list *commits = NULL, **tail = &commits, *iter;
+       struct commit_list *tips = NULL, **tips_tail = &tips;
+       struct commit *commit;
+       struct oidmap commit2todo = OIDMAP_INIT;
+       struct string_entry *entry;
+       struct oidset interesting = OIDSET_INIT, child_seen = OIDSET_INIT,
+               shown = OIDSET_INIT;
+       struct label_state state = { OIDMAP_INIT, { NULL }, STRBUF_INIT };
+
+       int abbr = flags & TODO_LIST_ABBREVIATE_CMDS;
+       const char *cmd_pick = abbr ? "p" : "pick",
+               *cmd_label = abbr ? "l" : "label",
+               *cmd_reset = abbr ? "t" : "reset",
+               *cmd_merge = abbr ? "m" : "merge";
+
+       oidmap_init(&commit2todo, 0);
+       oidmap_init(&state.commit2label, 0);
+       hashmap_init(&state.labels, (hashmap_cmp_fn) labels_cmp, NULL, 0);
+       strbuf_init(&state.buf, 32);
+
+       if (revs->cmdline.nr && (revs->cmdline.rev[0].flags & BOTTOM)) {
+               struct object_id *oid = &revs->cmdline.rev[0].item->oid;
+               FLEX_ALLOC_STR(entry, string, "onto");
+               oidcpy(&entry->entry.oid, oid);
+               oidmap_put(&state.commit2label, entry);
+       }
+
+       /*
+        * First phase:
+        * - get onelines for all commits
+        * - gather all branch tips (i.e. 2nd or later parents of merges)
+        * - label all branch tips
+        */
+       while ((commit = get_revision(revs))) {
+               struct commit_list *to_merge;
+               int is_octopus;
+               const char *p1, *p2;
+               struct object_id *oid;
+               int is_empty;
+
+               tail = &commit_list_insert(commit, tail)->next;
+               oidset_insert(&interesting, &commit->object.oid);
+
+               is_empty = is_original_commit_empty(commit);
+               if (!is_empty && (commit->object.flags & PATCHSAME))
+                       continue;
+
+               strbuf_reset(&oneline);
+               pretty_print_commit(pp, commit, &oneline);
+
+               to_merge = commit->parents ? commit->parents->next : NULL;
+               if (!to_merge) {
+                       /* non-merge commit: easy case */
+                       strbuf_reset(&buf);
+                       if (!keep_empty && is_empty)
+                               strbuf_addf(&buf, "%c ", comment_line_char);
+                       strbuf_addf(&buf, "%s %s %s", cmd_pick,
+                                   oid_to_hex(&commit->object.oid),
+                                   oneline.buf);
+
+                       FLEX_ALLOC_STR(entry, string, buf.buf);
+                       oidcpy(&entry->entry.oid, &commit->object.oid);
+                       oidmap_put(&commit2todo, entry);
+
+                       continue;
+               }
+
+               is_octopus = to_merge && to_merge->next;
+
+               if (is_octopus)
+                       BUG("Octopus merges not yet supported");
+
+               /* Create a label */
+               strbuf_reset(&label);
+               if (skip_prefix(oneline.buf, "Merge ", &p1) &&
+                   (p1 = strchr(p1, '\'')) &&
+                   (p2 = strchr(++p1, '\'')))
+                       strbuf_add(&label, p1, p2 - p1);
+               else if (skip_prefix(oneline.buf, "Merge pull request ",
+                                    &p1) &&
+                        (p1 = strstr(p1, " from ")))
+                       strbuf_addstr(&label, p1 + strlen(" from "));
+               else
+                       strbuf_addbuf(&label, &oneline);
+
+               for (p1 = label.buf; *p1; p1++)
+                       if (isspace(*p1))
+                               *(char *)p1 = '-';
+
+               strbuf_reset(&buf);
+               strbuf_addf(&buf, "%s -C %s",
+                           cmd_merge, oid_to_hex(&commit->object.oid));
+
+               /* label the tip of merged branch */
+               oid = &to_merge->item->object.oid;
+               strbuf_addch(&buf, ' ');
+
+               if (!oidset_contains(&interesting, oid))
+                       strbuf_addstr(&buf, label_oid(oid, NULL, &state));
+               else {
+                       tips_tail = &commit_list_insert(to_merge->item,
+                                                       tips_tail)->next;
+
+                       strbuf_addstr(&buf, label_oid(oid, label.buf, &state));
+               }
+               strbuf_addf(&buf, " # %s", oneline.buf);
+
+               FLEX_ALLOC_STR(entry, string, buf.buf);
+               oidcpy(&entry->entry.oid, &commit->object.oid);
+               oidmap_put(&commit2todo, entry);
+       }
+
+       /*
+        * Second phase:
+        * - label branch points
+        * - add HEAD to the branch tips
+        */
+       for (iter = commits; iter; iter = iter->next) {
+               struct commit_list *parent = iter->item->parents;
+               for (; parent; parent = parent->next) {
+                       struct object_id *oid = &parent->item->object.oid;
+                       if (!oidset_contains(&interesting, oid))
+                               continue;
+                       if (!oidset_contains(&child_seen, oid))
+                               oidset_insert(&child_seen, oid);
+                       else
+                               label_oid(oid, "branch-point", &state);
+               }
+
+               /* Add HEAD as implict "tip of branch" */
+               if (!iter->next)
+                       tips_tail = &commit_list_insert(iter->item,
+                                                       tips_tail)->next;
+       }
+
+       /*
+        * Third phase: output the todo list. This is a bit tricky, as we
+        * want to avoid jumping back and forth between revisions. To
+        * accomplish that goal, we walk backwards from the branch tips,
+        * gathering commits not yet shown, reversing the list on the fly,
+        * then outputting that list (labeling revisions as needed).
+        */
+       fprintf(out, "%s onto\n", cmd_label);
+       for (iter = tips; iter; iter = iter->next) {
+               struct commit_list *list = NULL, *iter2;
+
+               commit = iter->item;
+               if (oidset_contains(&shown, &commit->object.oid))
+                       continue;
+               entry = oidmap_get(&state.commit2label, &commit->object.oid);
+
+               if (entry)
+                       fprintf(out, "\n# Branch %s\n", entry->string);
+               else
+                       fprintf(out, "\n");
+
+               while (oidset_contains(&interesting, &commit->object.oid) &&
+                      !oidset_contains(&shown, &commit->object.oid)) {
+                       commit_list_insert(commit, &list);
+                       if (!commit->parents) {
+                               commit = NULL;
+                               break;
+                       }
+                       commit = commit->parents->item;
+               }
+
+               if (!commit)
+                       fprintf(out, "%s %s\n", cmd_reset,
+                               rebase_cousins ? "onto" : "[new root]");
+               else {
+                       const char *to = NULL;
+
+                       entry = oidmap_get(&state.commit2label,
+                                          &commit->object.oid);
+                       if (entry)
+                               to = entry->string;
+                       else if (!rebase_cousins)
+                               to = label_oid(&commit->object.oid, NULL,
+                                              &state);
+
+                       if (!to || !strcmp(to, "onto"))
+                               fprintf(out, "%s onto\n", cmd_reset);
+                       else {
+                               strbuf_reset(&oneline);
+                               pretty_print_commit(pp, commit, &oneline);
+                               fprintf(out, "%s %s # %s\n",
+                                       cmd_reset, to, oneline.buf);
+                       }
+               }
+
+               for (iter2 = list; iter2; iter2 = iter2->next) {
+                       struct object_id *oid = &iter2->item->object.oid;
+                       entry = oidmap_get(&commit2todo, oid);
+                       /* only show if not already upstream */
+                       if (entry)
+                               fprintf(out, "%s\n", entry->string);
+                       entry = oidmap_get(&state.commit2label, oid);
+                       if (entry)
+                               fprintf(out, "%s %s\n",
+                                       cmd_label, entry->string);
+                       oidset_insert(&shown, oid);
+               }
+
+               free_commit_list(list);
+       }
+
+       free_commit_list(commits);
+       free_commit_list(tips);
+
+       strbuf_release(&label);
+       strbuf_release(&oneline);
+       strbuf_release(&buf);
+
+       oidmap_free(&commit2todo, 1);
+       oidmap_free(&state.commit2label, 1);
+       hashmap_free(&state.labels, 1);
+       strbuf_release(&state.buf);
+
+       return 0;
+}
+
+int sequencer_make_script(FILE *out, int argc, const char **argv,
+                         unsigned flags)
+{
+       char *format = NULL;
+       struct pretty_print_context pp = {0};
+       struct strbuf buf = STRBUF_INIT;
+       struct rev_info revs;
+       struct commit *commit;
+       int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
+       const char *insn = flags & TODO_LIST_ABBREVIATE_CMDS ? "p" : "pick";
+       int rebase_merges = flags & TODO_LIST_REBASE_MERGES;
+
+       init_revisions(&revs, NULL);
+       revs.verbose_header = 1;
+       if (!rebase_merges)
+               revs.max_parents = 1;
+       revs.cherry_mark = 1;
+       revs.limited = 1;
+       revs.reverse = 1;
+       revs.right_only = 1;
+       revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
+       revs.topo_order = 1;
+
+       revs.pretty_given = 1;
+       git_config_get_string("rebase.instructionFormat", &format);
+       if (!format || !*format) {
+               free(format);
+               format = xstrdup("%s");
+       }
+       get_commit_format(format, &revs);
+       free(format);
+       pp.fmt = revs.commit_format;
+       pp.output_encoding = get_log_output_encoding();
+
+       if (setup_revisions(argc, argv, &revs, NULL) > 1)
+               return error(_("make_script: unhandled options"));
+
+       if (prepare_revision_walk(&revs) < 0)
+               return error(_("make_script: error preparing revisions"));
+
+       if (rebase_merges)
+               return make_script_with_merges(&pp, &revs, out, flags);
+
+       while ((commit = get_revision(&revs))) {
+               int is_empty  = is_original_commit_empty(commit);
+
+               if (!is_empty && (commit->object.flags & PATCHSAME))
+                       continue;
+               strbuf_reset(&buf);
+               if (!keep_empty && is_empty)
+                       strbuf_addf(&buf, "%c ", comment_line_char);
+               strbuf_addf(&buf, "%s %s ", insn,
+                           oid_to_hex(&commit->object.oid));
+               pretty_print_commit(&pp, commit, &buf);
+               strbuf_addch(&buf, '\n');
+               fputs(buf.buf, out);
+       }
+       strbuf_release(&buf);
+       return 0;
+}
+
+/*
+ * Add commands after pick and (series of) squash/fixup commands
+ * in the todo list.
+ */
+int sequencer_add_exec_commands(const char *commands)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct todo_item *item;
+       struct strbuf *buf = &todo_list.buf;
+       size_t offset = 0, commands_len = strlen(commands);
+       int i, first;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error(_("could not read '%s'."), todo_file);
+
+       if (parse_insn_buffer(todo_list.buf.buf, &todo_list)) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       first = 1;
+       /* insert <commands> before every pick except the first one */
+       for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
+               if (item->command == TODO_PICK && !first) {
+                       strbuf_insert(buf, item->offset_in_buf + offset,
+                                     commands, commands_len);
+                       offset += commands_len;
+               }
+               first = 0;
+       }
+
+       /* append final <commands> */
+       strbuf_add(buf, commands, commands_len);
+
+       i = write_message(buf->buf, buf->len, todo_file, 0);
+       todo_list_release(&todo_list);
+       return i;
+}
+
+int transform_todos(unsigned flags)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct strbuf buf = STRBUF_INIT;
+       struct todo_item *item;
+       int i;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error(_("could not read '%s'."), todo_file);
+
+       if (parse_insn_buffer(todo_list.buf.buf, &todo_list)) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
+               /* if the item is not a command write it and continue */
+               if (item->command >= TODO_COMMENT) {
+                       strbuf_addf(&buf, "%.*s\n", item->arg_len, item->arg);
+                       continue;
+               }
+
+               /* add command to the buffer */
+               if (flags & TODO_LIST_ABBREVIATE_CMDS)
+                       strbuf_addch(&buf, command_to_char(item->command));
+               else
+                       strbuf_addstr(&buf, command_to_string(item->command));
+
+               /* add commit id */
+               if (item->commit) {
+                       const char *oid = flags & TODO_LIST_SHORTEN_IDS ?
+                                         short_commit_name(item->commit) :
+                                         oid_to_hex(&item->commit->object.oid);
+
+                       if (item->command == TODO_MERGE) {
+                               if (item->flags & TODO_EDIT_MERGE_MSG)
+                                       strbuf_addstr(&buf, " -c");
+                               else
+                                       strbuf_addstr(&buf, " -C");
+                       }
+
+                       strbuf_addf(&buf, " %s", oid);
+               }
+
+               /* add all the rest */
+               if (!item->arg_len)
+                       strbuf_addch(&buf, '\n');
+               else
+                       strbuf_addf(&buf, " %.*s\n", item->arg_len, item->arg);
+       }
+
+       i = write_message(buf.buf, buf.len, todo_file, 0);
+       todo_list_release(&todo_list);
+       return i;
+}
+
+enum check_level {
+       CHECK_IGNORE = 0, CHECK_WARN, CHECK_ERROR
+};
+
+static enum check_level get_missing_commit_check_level(void)
+{
+       const char *value;
+
+       if (git_config_get_value("rebase.missingcommitscheck", &value) ||
+                       !strcasecmp("ignore", value))
+               return CHECK_IGNORE;
+       if (!strcasecmp("warn", value))
+               return CHECK_WARN;
+       if (!strcasecmp("error", value))
+               return CHECK_ERROR;
+       warning(_("unrecognized setting %s for option "
+                 "rebase.missingCommitsCheck. Ignoring."), value);
+       return CHECK_IGNORE;
+}
+
+define_commit_slab(commit_seen, unsigned char);
+/*
+ * Check if the user dropped some commits by mistake
+ * Behaviour determined by rebase.missingCommitsCheck.
+ * Check if there is an unrecognized command or a
+ * bad SHA-1 in a command.
+ */
+int check_todo_list(void)
+{
+       enum check_level check_level = get_missing_commit_check_level();
+       struct strbuf todo_file = STRBUF_INIT;
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct strbuf missing = STRBUF_INIT;
+       int advise_to_edit_todo = 0, res = 0, i;
+       struct commit_seen commit_seen;
+
+       init_commit_seen(&commit_seen);
+
+       strbuf_addstr(&todo_file, rebase_path_todo());
+       if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
+               res = -1;
+               goto leave_check;
+       }
+       advise_to_edit_todo = res =
+               parse_insn_buffer(todo_list.buf.buf, &todo_list);
+
+       if (res || check_level == CHECK_IGNORE)
+               goto leave_check;
+
+       /* Mark the commits in git-rebase-todo as seen */
+       for (i = 0; i < todo_list.nr; i++) {
+               struct commit *commit = todo_list.items[i].commit;
+               if (commit)
+                       *commit_seen_at(&commit_seen, commit) = 1;
+       }
+
+       todo_list_release(&todo_list);
+       strbuf_addstr(&todo_file, ".backup");
+       if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
+               res = -1;
+               goto leave_check;
+       }
+       strbuf_release(&todo_file);
+       res = !!parse_insn_buffer(todo_list.buf.buf, &todo_list);
+
+       /* Find commits in git-rebase-todo.backup yet unseen */
+       for (i = todo_list.nr - 1; i >= 0; i--) {
+               struct todo_item *item = todo_list.items + i;
+               struct commit *commit = item->commit;
+               if (commit && !*commit_seen_at(&commit_seen, commit)) {
+                       strbuf_addf(&missing, " - %s %.*s\n",
+                                   short_commit_name(commit),
+                                   item->arg_len, item->arg);
+                       *commit_seen_at(&commit_seen, commit) = 1;
+               }
+       }
+
+       /* Warn about missing commits */
+       if (!missing.len)
+               goto leave_check;
+
+       if (check_level == CHECK_ERROR)
+               advise_to_edit_todo = res = 1;
+
+       fprintf(stderr,
+               _("Warning: some commits may have been dropped accidentally.\n"
+               "Dropped commits (newer to older):\n"));
+
+       /* Make the list user-friendly and display */
+       fputs(missing.buf, stderr);
+       strbuf_release(&missing);
+
+       fprintf(stderr, _("To avoid this message, use \"drop\" to "
+               "explicitly remove a commit.\n\n"
+               "Use 'git config rebase.missingCommitsCheck' to change "
+               "the level of warnings.\n"
+               "The possible behaviours are: ignore, warn, error.\n\n"));
+
+leave_check:
+       clear_commit_seen(&commit_seen);
+       strbuf_release(&todo_file);
+       todo_list_release(&todo_list);
+
+       if (advise_to_edit_todo)
+               fprintf(stderr,
+                       _("You can fix this with 'git rebase --edit-todo' "
+                         "and then run 'git rebase --continue'.\n"
+                         "Or you can abort the rebase with 'git rebase"
+                         " --abort'.\n"));
+
+       return res;
+}
+
+static int rewrite_file(const char *path, const char *buf, size_t len)
+{
+       int rc = 0;
+       int fd = open(path, O_WRONLY | O_TRUNC);
+       if (fd < 0)
+               return error_errno(_("could not open '%s' for writing"), path);
+       if (write_in_full(fd, buf, len) < 0)
+               rc = error_errno(_("could not write to '%s'"), path);
+       if (close(fd) && !rc)
+               rc = error_errno(_("could not close '%s'"), path);
+       return rc;
+}
+
+/* skip picking commits whose parents are unchanged */
+int skip_unnecessary_picks(void)
+{
+       const char *todo_file = rebase_path_todo();
+       struct strbuf buf = STRBUF_INIT;
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct object_id onto_oid, *oid = &onto_oid, *parent_oid;
+       int fd, i;
+
+       if (!read_oneliner(&buf, rebase_path_onto(), 0))
+               return error(_("could not read 'onto'"));
+       if (get_oid(buf.buf, &onto_oid)) {
+               strbuf_release(&buf);
+               return error(_("need a HEAD to fixup"));
+       }
+       strbuf_release(&buf);
+
+       if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
+               return -1;
+       if (parse_insn_buffer(todo_list.buf.buf, &todo_list) < 0) {
+               todo_list_release(&todo_list);
+               return -1;
+       }
+
+       for (i = 0; i < todo_list.nr; i++) {
+               struct todo_item *item = todo_list.items + i;
+
+               if (item->command >= TODO_NOOP)
+                       continue;
+               if (item->command != TODO_PICK)
+                       break;
+               if (parse_commit(item->commit)) {
+                       todo_list_release(&todo_list);
+                       return error(_("could not parse commit '%s'"),
+                               oid_to_hex(&item->commit->object.oid));
+               }
+               if (!item->commit->parents)
+                       break; /* root commit */
+               if (item->commit->parents->next)
+                       break; /* merge commit */
+               parent_oid = &item->commit->parents->item->object.oid;
+               if (hashcmp(parent_oid->hash, oid->hash))
+                       break;
+               oid = &item->commit->object.oid;
+       }
+       if (i > 0) {
+               int offset = get_item_line_offset(&todo_list, i);
+               const char *done_path = rebase_path_done();
+
+               fd = open(done_path, O_CREAT | O_WRONLY | O_APPEND, 0666);
+               if (fd < 0) {
+                       error_errno(_("could not open '%s' for writing"),
+                                   done_path);
+                       todo_list_release(&todo_list);
+                       return -1;
+               }
+               if (write_in_full(fd, todo_list.buf.buf, offset) < 0) {
+                       error_errno(_("could not write to '%s'"), done_path);
+                       todo_list_release(&todo_list);
+                       close(fd);
+                       return -1;
+               }
+               close(fd);
+
+               if (rewrite_file(rebase_path_todo(), todo_list.buf.buf + offset,
+                                todo_list.buf.len - offset) < 0) {
+                       todo_list_release(&todo_list);
+                       return -1;
+               }
+
+               todo_list.current = i;
+               if (is_fixup(peek_command(&todo_list, 0)))
+                       record_in_rewritten(oid, peek_command(&todo_list, 0));
+       }
+
+       todo_list_release(&todo_list);
+       printf("%s\n", oid_to_hex(oid));
+
+       return 0;
+}
+
+struct subject2item_entry {
+       struct hashmap_entry entry;
+       int i;
+       char subject[FLEX_ARRAY];
+};
+
+static int subject2item_cmp(const void *fndata,
+                           const struct subject2item_entry *a,
+                           const struct subject2item_entry *b, const void *key)
+{
+       return key ? strcmp(a->subject, key) : strcmp(a->subject, b->subject);
+}
+
+define_commit_slab(commit_todo_item, struct todo_item *);
+
+/*
+ * Rearrange the todo list that has both "pick commit-id msg" and "pick
+ * commit-id fixup!/squash! msg" in it so that the latter is put immediately
+ * after the former, and change "pick" to "fixup"/"squash".
+ *
+ * Note that if the config has specified a custom instruction format, each log
+ * message will have to be retrieved from the commit (as the oneline in the
+ * script cannot be trusted) in order to normalize the autosquash arrangement.
+ */
+int rearrange_squash(void)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct hashmap subject2item;
+       int res = 0, rearranged = 0, *next, *tail, i;
+       char **subjects;
+       struct commit_todo_item commit_todo;
+
+       if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
+               return -1;
+       if (parse_insn_buffer(todo_list.buf.buf, &todo_list) < 0) {
+               todo_list_release(&todo_list);
+               return -1;
+       }
+
+       init_commit_todo_item(&commit_todo);
+       /*
+        * The hashmap maps onelines to the respective todo list index.
+        *
+        * If any items need to be rearranged, the next[i] value will indicate
+        * which item was moved directly after the i'th.
+        *
+        * In that case, last[i] will indicate the index of the latest item to
+        * be moved to appear after the i'th.
+        */
+       hashmap_init(&subject2item, (hashmap_cmp_fn) subject2item_cmp,
+                    NULL, todo_list.nr);
+       ALLOC_ARRAY(next, todo_list.nr);
+       ALLOC_ARRAY(tail, todo_list.nr);
+       ALLOC_ARRAY(subjects, todo_list.nr);
+       for (i = 0; i < todo_list.nr; i++) {
+               struct strbuf buf = STRBUF_INIT;
+               struct todo_item *item = todo_list.items + i;
+               const char *commit_buffer, *subject, *p;
+               size_t subject_len;
+               int i2 = -1;
+               struct subject2item_entry *entry;
+
+               next[i] = tail[i] = -1;
+               if (!item->commit || item->command == TODO_DROP) {
+                       subjects[i] = NULL;
+                       continue;
+               }
+
+               if (is_fixup(item->command)) {
+                       todo_list_release(&todo_list);
+                       clear_commit_todo_item(&commit_todo);
+                       return error(_("the script was already rearranged."));
+               }
+
+               *commit_todo_item_at(&commit_todo, item->commit) = item;
+
+               parse_commit(item->commit);
+               commit_buffer = get_commit_buffer(item->commit, NULL);
+               find_commit_subject(commit_buffer, &subject);
+               format_subject(&buf, subject, " ");
+               subject = subjects[i] = strbuf_detach(&buf, &subject_len);
+               unuse_commit_buffer(item->commit, commit_buffer);
+               if ((skip_prefix(subject, "fixup! ", &p) ||
+                    skip_prefix(subject, "squash! ", &p))) {
+                       struct commit *commit2;
+
+                       for (;;) {
+                               while (isspace(*p))
+                                       p++;
+                               if (!skip_prefix(p, "fixup! ", &p) &&
+                                   !skip_prefix(p, "squash! ", &p))
+                                       break;
+                       }
+
+                       if ((entry = hashmap_get_from_hash(&subject2item,
+                                                          strhash(p), p)))
+                               /* found by title */
+                               i2 = entry->i;
+                       else if (!strchr(p, ' ') &&
+                                (commit2 =
+                                 lookup_commit_reference_by_name(p)) &&
+                                *commit_todo_item_at(&commit_todo, commit2))
+                               /* found by commit name */
+                               i2 = *commit_todo_item_at(&commit_todo, commit2)
+                                       - todo_list.items;
+                       else {
+                               /* copy can be a prefix of the commit subject */
+                               for (i2 = 0; i2 < i; i2++)
+                                       if (subjects[i2] &&
+                                           starts_with(subjects[i2], p))
+                                               break;
+                               if (i2 == i)
+                                       i2 = -1;
+                       }
+               }
+               if (i2 >= 0) {
+                       rearranged = 1;
+                       todo_list.items[i].command =
+                               starts_with(subject, "fixup!") ?
+                               TODO_FIXUP : TODO_SQUASH;
+                       if (next[i2] < 0)
+                               next[i2] = i;
+                       else
+                               next[tail[i2]] = i;
+                       tail[i2] = i;
+               } else if (!hashmap_get_from_hash(&subject2item,
+                                               strhash(subject), subject)) {
+                       FLEX_ALLOC_MEM(entry, subject, subject, subject_len);
+                       entry->i = i;
+                       hashmap_entry_init(entry, strhash(entry->subject));
+                       hashmap_put(&subject2item, entry);
+               }
+       }
+
+       if (rearranged) {
+               struct strbuf buf = STRBUF_INIT;
+
+               for (i = 0; i < todo_list.nr; i++) {
+                       enum todo_command command = todo_list.items[i].command;
+                       int cur = i;
+
+                       /*
+                        * Initially, all commands are 'pick's. If it is a
+                        * fixup or a squash now, we have rearranged it.
+                        */
+                       if (is_fixup(command))
+                               continue;
+
+                       while (cur >= 0) {
+                               const char *bol =
+                                       get_item_line(&todo_list, cur);
+                               const char *eol =
+                                       get_item_line(&todo_list, cur + 1);
+
+                               /* replace 'pick', by 'fixup' or 'squash' */
+                               command = todo_list.items[cur].command;
+                               if (is_fixup(command)) {
+                                       strbuf_addstr(&buf,
+                                               todo_command_info[command].str);
+                                       bol += strcspn(bol, " \t");
+                               }
+
+                               strbuf_add(&buf, bol, eol - bol);
+
+                               cur = next[cur];
+                       }
+               }
+
+               res = rewrite_file(todo_file, buf.buf, buf.len);
+               strbuf_release(&buf);
+       }
+
+       free(next);
+       free(tail);
+       for (i = 0; i < todo_list.nr; i++)
+               free(subjects[i]);
+       free(subjects);
+       hashmap_free(&subject2item, 1);
+       todo_list_release(&todo_list);
+
+       clear_commit_todo_item(&commit_todo);
+       return res;
+}