t6044: add more testcases with staged changes before a merge is invoked
[gitweb.git] / sequencer.c
index e0e66b987b27072da4aea6304a565ab708be91e4..f9d1001dee9ad10e243aaeafc46fbdd13597fce7 100644 (file)
@@ -1,10 +1,10 @@
 #include "cache.h"
 #include "config.h"
 #include "lockfile.h"
-#include "sequencer.h"
 #include "dir.h"
 #include "object.h"
 #include "commit.h"
+#include "sequencer.h"
 #include "tag.h"
 #include "run-command.h"
 #include "exec_cmd.h"
 #include "trailer.h"
 #include "log-tree.h"
 #include "wt-status.h"
+#include "hashmap.h"
+#include "notes-utils.h"
+#include "sigchain.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")
@@ -129,6 +134,51 @@ 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);
+
+               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;
@@ -203,7 +253,7 @@ int sequencer_remove_state(struct replay_opts *opts)
                free(opts->xopts[i]);
        free(opts->xopts);
 
-       strbuf_addf(&dir, "%s", get_dir(opts));
+       strbuf_addstr(&dir, get_dir(opts));
        remove_dir_recursively(&dir, 0);
        strbuf_release(&dir);
 
@@ -289,7 +339,7 @@ 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)
@@ -302,10 +352,8 @@ static int write_message(const void *buf, size_t len, const char *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);
-       }
+       if (commit_lock_file(&msg_file) < 0)
+               return error(_("failed to finalize '%s'"), filename);
 
        return 0;
 }
@@ -346,7 +394,7 @@ 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 +440,7 @@ 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 ? &null_oid : from,
                                   0, sb.buf, &err) ||
            ref_transaction_commit(transaction, &err)) {
                ref_transaction_free(transaction);
@@ -435,9 +483,10 @@ 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();
 
@@ -447,6 +496,7 @@ 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();
@@ -461,21 +511,20 @@ 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);
@@ -488,8 +537,8 @@ static int is_index_unchanged(void)
        struct object_id head_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);
 
@@ -509,7 +558,7 @@ static int is_index_unchanged(void)
 
        if (!cache_tree_fully_valid(active_cache_tree))
                if (cache_tree_update(&the_index, 0))
-                       return error(_("unable to update cache tree\n"));
+                       return error(_("unable to update cache tree"));
 
        return !oidcmp(&active_cache_tree->oid,
                       &head_commit->tree->object.oid);
@@ -592,6 +641,18 @@ 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;
+}
+
 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"
@@ -654,8 +715,6 @@ 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);
        if ((flags & CLEANUP_MSG))
@@ -690,24 +749,479 @@ 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.hash, 0, NULL)) {
+               res = error(_("git write-tree failed to write a tree"));
+               goto out;
+       }
+
+       if (!(flags & ALLOW_EMPTY) && !oidcmp(current_head ?
+                                             &current_head->tree->object.oid :
+                                             &empty_tree_oid, &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;
+       }
+
+       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)) {
+               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());
+                       unlink(git_path_merge_msg());
+                       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 = &parent->tree->object.oid;
        } 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, &commit->tree->object.oid);
 }
 
 /*
@@ -793,6 +1307,13 @@ 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;
@@ -897,18 +1418,18 @@ static int update_squash_messages(enum todo_command command,
 
 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;
@@ -941,6 +1462,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
        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;
@@ -957,8 +1479,9 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
        } 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))
+                       oidcpy(&head, the_hash_algo->empty_tree);
+               if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD",
+                                      NULL, 0))
                        return error_dirty_index(opts);
        }
        discard_cache();
@@ -1001,9 +1524,7 @@ 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 +1577,8 @@ 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)
@@ -1081,6 +1604,9 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                }
        }
 
+       if (opts->signoff)
+               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) {
@@ -1114,12 +1640,12 @@ 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) {
@@ -1138,9 +1664,13 @@ 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());
@@ -1149,6 +1679,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
 
 leave:
        free_message(commit, &msg);
+       free(author);
        update_abort_safety_file();
 
        return res;
@@ -1173,7 +1704,7 @@ 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);
@@ -1181,14 +1712,13 @@ 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;
 }
 
@@ -1252,20 +1782,26 @@ 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) {
+               item->commit = NULL;
                item->arg = bol;
                item->arg_len = (int)(eol - bol);
                return 0;
@@ -1332,22 +1868,31 @@ static int count_commands(struct todo_list *todo_list)
        return count;
 }
 
+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)
@@ -1562,25 +2107,24 @@ 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) {
+       written = write_in_full(fd, buf.buf, buf.len);
+       strbuf_release(&buf);
+       if (written < 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) {
-               rollback_lock_file(&head_lock);
-               return error(_("failed to finalize '%s'."), git_path_head_file());
-       }
+       if (commit_lock_file(&head_lock) < 0)
+               return error(_("failed to finalize '%s'"), git_path_head_file());
        return 0;
 }
 
@@ -1608,36 +2152,37 @@ 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()))
                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 +2202,12 @@ 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 +2217,7 @@ 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 +2228,7 @@ 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;
 
@@ -1703,7 +2248,7 @@ static int save_todo(struct todo_list *todo_list, struct replay_opts *opts)
                        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();
@@ -1773,6 +2318,9 @@ 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 +2354,13 @@ 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);
 }
 
@@ -1857,12 +2405,15 @@ static int error_failed_squash(struct commit *commit,
 
 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)
@@ -1892,6 +2443,8 @@ static int do_exec(const char *command_line)
                status = 1;
        }
 
+       argv_array_clear(&child_env);
+
        return status;
 }
 
@@ -2019,6 +2572,7 @@ 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))
@@ -2097,10 +2651,10 @@ 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 +2662,7 @@ 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 +2673,8 @@ 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 +2701,8 @@ 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);
@@ -2223,16 +2777,16 @@ static int commit_staged_changes(struct replay_opts *opts)
 
        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 (oidcmp(&head, &to_amend))
                        return error(_("\nYou have uncommitted changes in your "
                                       "working tree. Please, commit them\n"
                                       "first and then run 'git rebase "
@@ -2274,7 +2828,7 @@ int sequencer_continue(struct replay_opts *opts)
                        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 +2838,7 @@ 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);
        }
@@ -2324,7 +2878,7 @@ int sequencer_pick_revisions(struct replay_opts *opts)
                        if (!lookup_commit_reference_gently(&oid, 1)) {
                                enum object_type type = sha1_object_info(oid.hash, 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 +2985,528 @@ void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
 
        strbuf_release(&sob);
 }
+
+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";
+
+       init_revisions(&revs, NULL);
+       revs.verbose_header = 1;
+       revs.max_parents = 1;
+       revs.cherry_pick = 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"));
+
+       while ((commit = get_revision(&revs))) {
+               strbuf_reset(&buf);
+               if (!keep_empty && is_original_commit_empty(commit))
+                       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);
+
+                       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;
+}
+
+/*
+ * 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;
+
+       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->util = (void *)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->util) {
+                       strbuf_addf(&missing, " - %s %.*s\n",
+                                   short_commit_name(commit),
+                                   item->arg_len, item->arg);
+                       commit->util = (void *)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:
+       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 = i < todo_list.nr ?
+                       todo_list.items[i].offset_in_buf : todo_list.buf.len;
+               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);
+}
+
+/*
+ * 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;
+
+       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;
+       }
+
+       /*
+        * 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->command >= TODO_EXEC) {
+                       subjects[i] = NULL;
+                       continue;
+               }
+
+               if (is_fixup(item->command)) {
+                       todo_list_release(&todo_list);
+                       return error(_("the script was already rearranged."));
+               }
+
+               item->commit->util = 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)) &&
+                                commit2->util)
+                               /* found by commit name */
+                               i2 = (struct todo_item *)commit2->util
+                                       - 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) {
+                               int offset = todo_list.items[cur].offset_in_buf;
+                               int end_offset = cur + 1 < todo_list.nr ?
+                                       todo_list.items[cur + 1].offset_in_buf :
+                                       todo_list.buf.len;
+                               char *bol = todo_list.buf.buf + offset;
+                               char *eol = todo_list.buf.buf + end_offset;
+
+                               /* 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);
+
+       return res;
+}