Merge branch 'jk/rebase-i-exec-gitdir-fix' into maint
[gitweb.git] / sequencer.c
index 689d9a311731411fa5a0bb3710f7a31c82bc7ba8..332a383b037d2a24627a2c833aae163dc05665f8 100644 (file)
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "config.h"
 #include "lockfile.h"
 #include "sequencer.h"
 #include "dir.h"
@@ -19,6 +20,7 @@
 #include "trailer.h"
 #include "log-tree.h"
 #include "wt-status.h"
+#include "hashmap.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
@@ -126,6 +128,7 @@ static GIT_PATH_FUNC(rebase_path_onto, "rebase-merge/onto")
 static GIT_PATH_FUNC(rebase_path_autostash, "rebase-merge/autostash")
 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 inline int is_rebase_i(const struct replay_opts *opts)
 {
@@ -201,7 +204,7 @@ 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);
 
@@ -344,7 +347,7 @@ static int read_oneliner(struct strbuf *buf,
 
 static struct tree *empty_tree(void)
 {
-       return lookup_tree(EMPTY_TREE_SHA1_BIN);
+       return lookup_tree(&empty_tree_oid);
 }
 
 static int error_dirty_index(struct replay_opts *opts)
@@ -374,7 +377,7 @@ static void update_abort_safety_file(void)
                write_file(git_path_abort_safety_file(), "%s", "");
 }
 
-static int fast_forward_to(const unsigned char *to, const unsigned char *from,
+static int fast_forward_to(const struct object_id *to, const struct object_id *from,
                        int unborn, struct replay_opts *opts)
 {
        struct ref_transaction *transaction;
@@ -390,7 +393,7 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from,
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
            ref_transaction_update(transaction, "HEAD",
-                                  to, unborn ? null_sha1 : from,
+                                  to->hash, unborn ? null_sha1 : from->hash,
                                   0, sb.buf, &err) ||
            ref_transaction_commit(transaction, &err)) {
                ref_transaction_free(transaction);
@@ -426,7 +429,7 @@ void append_conflicts_hint(struct strbuf *msgbuf)
 
 static int do_recursive_merge(struct commit *base, struct commit *next,
                              const char *base_label, const char *next_label,
-                             unsigned char *head, struct strbuf *msgbuf,
+                             struct object_id *head, struct strbuf *msgbuf,
                              struct replay_opts *opts)
 {
        struct merge_options o;
@@ -464,7 +467,8 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 
        if (active_cache_changed &&
            write_locked_index(&the_index, &index_lock, COMMIT_LOCK))
-               /* TRANSLATORS: %s will be "revert", "cherry-pick" or
+               /*
+                * TRANSLATORS: %s will be "revert", "cherry-pick" or
                 * "rebase -i".
                 */
                return error(_("%s: Unable to write new index file"),
@@ -482,13 +486,13 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 
 static int is_index_unchanged(void)
 {
-       unsigned char head_sha1[20];
+       struct object_id head_oid;
        struct commit *head_commit;
 
-       if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_sha1, NULL))
+       if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_oid.hash, NULL))
                return error(_("could not resolve HEAD commit\n"));
 
-       head_commit = lookup_commit(head_sha1);
+       head_commit = lookup_commit(&head_oid);
 
        /*
         * If head_commit is NULL, check_commit, called from
@@ -508,7 +512,8 @@ static int is_index_unchanged(void)
                if (cache_tree_update(&the_index, 0))
                        return error(_("unable to update cache tree\n"));
 
-       return !hashcmp(active_cache_tree->sha1, head_commit->tree->object.oid.hash);
+       return !oidcmp(&active_cache_tree->oid,
+                      &head_commit->tree->object.oid);
 }
 
 static int write_author_script(const char *message)
@@ -602,6 +607,12 @@ N_("you have staged changes in your working tree\n"
 "\n"
 "  git rebase --continue\n");
 
+#define ALLOW_EMPTY (1<<0)
+#define EDIT_MSG    (1<<1)
+#define AMEND_MSG   (1<<2)
+#define CLEANUP_MSG (1<<3)
+#define VERIFY_MSG  (1<<4)
+
 /*
  * If we are cherry-pick, and if the merge did not result in
  * hand-editing, we will hit this commit and inherit the original
@@ -615,8 +626,7 @@ N_("you have staged changes in your working tree\n"
  * author metadata.
  */
 static int run_git_commit(const char *defmsg, struct replay_opts *opts,
-                         int allow_empty, int edit, int amend,
-                         int cleanup_commit_message)
+                         unsigned int flags)
 {
        struct child_process cmd = CHILD_PROCESS_INIT;
        const char *value;
@@ -624,7 +634,7 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
        cmd.git_cmd = 1;
 
        if (is_rebase_i(opts)) {
-               if (!edit) {
+               if (!(flags & EDIT_MSG)) {
                        cmd.stdout_to_stderr = 1;
                        cmd.err = -1;
                }
@@ -638,9 +648,10 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
        }
 
        argv_array_push(&cmd.args, "commit");
-       argv_array_push(&cmd.args, "-n");
 
-       if (amend)
+       if (!(flags & VERIFY_MSG))
+               argv_array_push(&cmd.args, "-n");
+       if ((flags & AMEND_MSG))
                argv_array_push(&cmd.args, "--amend");
        if (opts->gpg_sign)
                argv_array_pushf(&cmd.args, "-S%s", opts->gpg_sign);
@@ -648,16 +659,16 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
                argv_array_push(&cmd.args, "-s");
        if (defmsg)
                argv_array_pushl(&cmd.args, "-F", defmsg, NULL);
-       if (cleanup_commit_message)
+       if ((flags & CLEANUP_MSG))
                argv_array_push(&cmd.args, "--cleanup=strip");
-       if (edit)
+       if ((flags & EDIT_MSG))
                argv_array_push(&cmd.args, "-e");
-       else if (!cleanup_commit_message &&
+       else if (!(flags & CLEANUP_MSG) &&
                 !opts->signoff && !opts->record_origin &&
                 git_config_get_value("commit.cleanup", &value))
                argv_array_push(&cmd.args, "--cleanup=verbatim");
 
-       if (allow_empty)
+       if ((flags & ALLOW_EMPTY))
                argv_array_push(&cmd.args, "--allow-empty");
 
        if (opts->allow_empty_message)
@@ -682,7 +693,7 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
 
 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"),
@@ -692,12 +703,12 @@ static int is_original_commit_empty(struct commit *commit)
                if (parse_commit(parent))
                        return error(_("could not parse parent commit %s\n"),
                                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 = &empty_tree_oid; /* commit is root */
        }
 
-       return !hashcmp(ptree_sha1, commit->tree->object.oid.hash);
+       return !oidcmp(ptree_oid, &commit->tree->object.oid);
 }
 
 /*
@@ -828,13 +839,13 @@ static int update_squash_messages(enum todo_command command,
                strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
                strbuf_release(&header);
        } else {
-               unsigned char head[20];
+               struct object_id head;
                struct commit *head_commit;
                const char *head_message, *body;
 
-               if (get_sha1("HEAD", head))
+               if (get_oid("HEAD", &head))
                        return error(_("need a HEAD to fixup"));
-               if (!(head_commit = lookup_commit_reference(head)))
+               if (!(head_commit = lookup_commit_reference(&head)))
                        return error(_("could not read HEAD"));
                if (!(head_message = get_commit_buffer(head_commit, NULL)))
                        return error(_("could not read HEAD's commit message"));
@@ -887,18 +898,18 @@ 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) &&
-                       (out = fopen(rebase_path_rewritten_list(), "a"))) {
+       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;
@@ -911,7 +922,7 @@ static void flush_rewritten_pending(void) {
 
 static void record_in_rewritten(struct object_id *oid,
                enum todo_command next_command) {
-       FILE *out = fopen(rebase_path_rewritten_pending(), "a");
+       FILE *out = fopen_or_warn(rebase_path_rewritten_pending(), "a");
 
        if (!out)
                return;
@@ -926,14 +937,14 @@ static void record_in_rewritten(struct object_id *oid,
 static int do_pick_commit(enum todo_command command, struct commit *commit,
                struct replay_opts *opts, int final_fixup)
 {
-       int edit = opts->edit, cleanup_commit_message = 0;
-       const char *msg_file = edit ? NULL : git_path_merge_msg();
-       unsigned char head[20];
+       unsigned int flags = opts->edit ? EDIT_MSG : 0;
+       const char *msg_file = opts->edit ? NULL : git_path_merge_msg();
+       struct object_id head;
        struct commit *base, *next, *parent;
        const char *base_label, *next_label;
        struct commit_message msg = { NULL, NULL, NULL, NULL };
        struct strbuf msgbuf = STRBUF_INIT;
-       int res, unborn = 0, amend = 0, allow = 0;
+       int res, unborn = 0, allow;
 
        if (opts->no_commit) {
                /*
@@ -942,12 +953,12 @@ 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, 0, NULL))
+               if (write_cache_as_tree(head.hash, 0, NULL))
                        return error(_("your index file is unmerged."));
        } else {
-               unborn = get_sha1("HEAD", head);
+               unborn = get_oid("HEAD", &head);
                if (unborn)
-                       hashcpy(head, EMPTY_TREE_SHA1_BIN);
+                       oidcpy(&head, &empty_tree_oid);
                if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD", 0, 0))
                        return error_dirty_index(opts);
        }
@@ -983,15 +994,17 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        oid_to_hex(&commit->object.oid));
 
        if (opts->allow_ff && !is_fixup(command) &&
-           ((parent && !hashcmp(parent->object.oid.hash, head)) ||
+           ((parent && !oidcmp(&parent->object.oid, &head)) ||
             (!parent && unborn))) {
                if (is_rebase_i(opts))
                        write_author_script(msg.message);
-               res = fast_forward_to(commit->object.oid.hash, head, unborn,
+               res = fast_forward_to(&commit->object.oid, &head, unborn,
                        opts);
                if (res || command != TODO_REWORD)
                        goto leave;
-               edit = amend = 1;
+               flags |= EDIT_MSG | AMEND_MSG;
+               if (command == TODO_REWORD)
+                       flags |= VERIFY_MSG;
                msg_file = NULL;
                goto fast_forward_edit;
        }
@@ -1037,6 +1050,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        strbuf_addstr(&msgbuf, p);
 
                if (opts->record_origin) {
+                       strbuf_complete_line(&msgbuf);
                        if (!has_conforming_footer(&msgbuf, NULL, 0))
                                strbuf_addch(&msgbuf, '\n');
                        strbuf_addstr(&msgbuf, cherry_picked_prefix);
@@ -1046,25 +1060,25 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
        }
 
        if (command == TODO_REWORD)
-               edit = 1;
+               flags |= EDIT_MSG | VERIFY_MSG;
        else if (is_fixup(command)) {
                if (update_squash_messages(command, commit, opts))
                        return -1;
-               amend = 1;
+               flags |= AMEND_MSG;
                if (!final_fixup)
                        msg_file = rebase_path_squash_msg();
                else if (file_exists(rebase_path_fixup_msg())) {
-                       cleanup_commit_message = 1;
+                       flags |= CLEANUP_MSG;
                        msg_file = rebase_path_fixup_msg();
                } else {
-                       const char *dest = git_path("SQUASH_MSG");
+                       const char *dest = git_path_squash_msg();
                        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());
                        msg_file = dest;
-                       edit = 1;
+                       flags |= EDIT_MSG;
                }
        }
 
@@ -1072,7 +1086,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                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);
+                                        &head, &msgbuf, opts);
                if (res < 0)
                        return res;
                res |= write_message(msgbuf.buf, msgbuf.len,
@@ -1088,7 +1102,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                commit_list_insert(next, &remotes);
                res |= try_merge_command(opts->strategy,
                                         opts->xopts_nr, (const char **)opts->xopts,
-                                       common, sha1_to_hex(head), remotes);
+                                       common, oid_to_hex(&head), remotes);
                free_commit_list(common);
                free_commit_list(remotes);
        }
@@ -1123,11 +1137,11 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
        if (allow < 0) {
                res = allow;
                goto leave;
-       }
+       } else if (allow)
+               flags |= ALLOW_EMPTY;
        if (!opts->no_commit)
 fast_forward_edit:
-               res = run_git_commit(msg_file, opts, allow, edit, amend,
-                                    cleanup_commit_message);
+               res = run_git_commit(msg_file, opts, flags);
 
        if (!res && final_fixup) {
                unlink(rebase_path_fixup_msg());
@@ -1192,6 +1206,7 @@ struct todo_list {
        struct todo_item *items;
        int nr, alloc, current;
        int done_nr, total_nr;
+       struct stat_data stat;
 };
 
 #define TODO_LIST_INIT { STRBUF_INIT }
@@ -1199,8 +1214,7 @@ struct todo_list {
 static void todo_list_release(struct todo_list *todo_list)
 {
        strbuf_release(&todo_list->buf);
-       free(todo_list->items);
-       todo_list->items = NULL;
+       FREE_AND_NULL(todo_list->items);
        todo_list->nr = todo_list->alloc = 0;
 }
 
@@ -1212,7 +1226,7 @@ static struct todo_item *append_new_todo(struct todo_list *todo_list)
 
 static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
 {
-       unsigned char commit_sha1[20];
+       struct object_id commit_oid;
        char *end_of_object_name;
        int i, saved, status, padding;
 
@@ -1261,7 +1275,7 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
        end_of_object_name = (char *) bol + strcspn(bol, " \t\n");
        saved = *end_of_object_name;
        *end_of_object_name = '\0';
-       status = get_sha1(bol, commit_sha1);
+       status = get_oid(bol, &commit_oid);
        *end_of_object_name = saved;
 
        item->arg = end_of_object_name + strspn(end_of_object_name, " \t");
@@ -1270,7 +1284,7 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
        if (status < 0)
                return -1;
 
-       item->commit = lookup_commit_reference(commit_sha1);
+       item->commit = lookup_commit_reference(&commit_oid);
        return !item->commit;
 }
 
@@ -1322,6 +1336,7 @@ static int count_commands(struct todo_list *todo_list)
 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;
 
@@ -1335,6 +1350,11 @@ static int read_populate_todo(struct todo_list *todo_list,
        }
        close(fd);
 
+       res = stat(todo_file, &st);
+       if (res)
+               return error(_("could not stat '%s'"), todo_file);
+       fill_stat_data(&todo_list->stat, &st);
+
        res = parse_insn_buffer(todo_list->buf.buf, todo_list);
        if (res) {
                if (is_rebase_i(opts))
@@ -1363,7 +1383,7 @@ static int read_populate_todo(struct todo_list *todo_list,
 
        if (is_rebase_i(opts)) {
                struct todo_list done = TODO_LIST_INIT;
-               FILE *f = fopen(rebase_path_msgtotal(), "w");
+               FILE *f = fopen_or_warn(rebase_path_msgtotal(), "w");
 
                if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
                                !parse_insn_buffer(done.buf.buf, &done))
@@ -1420,7 +1440,11 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
        else if (!strcmp(key, "options.strategy-option")) {
                ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
                opts->xopts[opts->xopts_nr++] = xstrdup(value);
-       } else
+       } else if (!strcmp(key, "options.allow-rerere-auto"))
+               opts->allow_rerere_auto =
+                       git_config_bool_or_int(key, value, &error_flag) ?
+                               RERERE_AUTOUPDATE : RERERE_NOAUTOUPDATE;
+       else
                return error(_("invalid key: %s"), key);
 
        if (!error_flag)
@@ -1461,6 +1485,15 @@ static int read_populate_opts(struct replay_opts *opts)
                                free(opts->gpg_sign);
                                opts->gpg_sign = xstrdup(buf.buf + 2);
                        }
+                       strbuf_reset(&buf);
+               }
+
+               if (read_oneliner(&buf, rebase_path_allow_rerere_autoupdate(), 1)) {
+                       if (!strcmp(buf.buf, "--rerere-autoupdate"))
+                               opts->allow_rerere_auto = RERERE_AUTOUPDATE;
+                       else if (!strcmp(buf.buf, "--no-rerere-autoupdate"))
+                               opts->allow_rerere_auto = RERERE_NOAUTOUPDATE;
+                       strbuf_reset(&buf);
                }
 
                if (file_exists(rebase_path_verbose()))
@@ -1533,6 +1566,7 @@ static int save_head(const char *head)
        static struct lock_file head_lock;
        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) {
@@ -1540,7 +1574,9 @@ static int save_head(const char *head)
                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());
@@ -1576,36 +1612,37 @@ 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.hash, 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) {
@@ -1625,12 +1662,12 @@ 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;
        }
@@ -1640,7 +1677,7 @@ 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);
@@ -1724,6 +1761,10 @@ static int save_opts(struct replay_opts *opts)
                                                        "options.strategy-option",
                                                        opts->xopts[i], "^$", 0);
        }
+       if (opts->allow_rerere_auto)
+               res |= git_config_set_in_file_gently(opts_file, "options.allow-rerere-auto",
+                                                    opts->allow_rerere_auto == RERERE_AUTOUPDATE ?
+                                                    "true" : "false");
        return res;
 }
 
@@ -1770,13 +1811,13 @@ 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);
 }
 
@@ -1812,10 +1853,10 @@ static int error_failed_squash(struct commit *commit,
                return error(_("could not rename '%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());
+       if (copy_file(git_path_merge_msg(), 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());
        return error_with_patch(commit, subject, subject_len, opts, 1, 0);
 }
 
@@ -1903,11 +1944,13 @@ static int apply_autostash(struct replay_opts *opts)
        strbuf_trim(&stash_sha1);
 
        child.git_cmd = 1;
+       child.no_stdout = 1;
+       child.no_stderr = 1;
        argv_array_push(&child.args, "stash");
        argv_array_push(&child.args, "apply");
        argv_array_push(&child.args, stash_sha1.buf);
        if (!run_command(&child))
-               printf(_("Applied autostash."));
+               fprintf(stderr, _("Applied autostash.\n"));
        else {
                struct child_process store = CHILD_PROCESS_INIT;
 
@@ -1921,10 +1964,11 @@ static int apply_autostash(struct replay_opts *opts)
                if (run_command(&store))
                        ret = error(_("cannot store %s"), stash_sha1.buf);
                else
-                       printf(_("Applying autostash resulted in conflicts.\n"
-                               "Your changes are safe in the stash.\n"
-                               "You can run \"git stash pop\" or"
-                               " \"git stash drop\" at any time.\n"));
+                       fprintf(stderr,
+                               _("Applying autostash resulted in conflicts.\n"
+                                 "Your changes are safe in the stash.\n"
+                                 "You can run \"git stash pop\" or"
+                                 " \"git stash drop\" at any time.\n"));
        }
 
        strbuf_release(&stash_sha1);
@@ -2002,7 +2046,8 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                        if (item->command == TODO_EDIT) {
                                struct commit *commit = item->commit;
                                if (!res)
-                                       warning(_("stopped at %s... %.*s"),
+                                       fprintf(stderr,
+                                               _("Stopped at %s...  %.*s\n"),
                                                short_commit_name(commit),
                                                item->arg_len, item->arg);
                                return error_with_patch(commit,
@@ -2024,10 +2069,25 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                } else if (item->command == TODO_EXEC) {
                        char *end_of_arg = (char *)(item->arg + item->arg_len);
                        int saved = *end_of_arg;
+                       struct stat st;
 
                        *end_of_arg = '\0';
                        res = do_exec(item->arg);
                        *end_of_arg = saved;
+
+                       /* Reread the todo file if it has changed. */
+                       if (res)
+                               ; /* fall through */
+                       else if (stat(get_todo_path(opts), &st))
+                               res = error_errno(_("could not stat '%s'"),
+                                                 get_todo_path(opts));
+                       else if (match_stat_data(&todo_list->stat, &st)) {
+                               todo_list_release(todo_list);
+                               if (read_populate_todo(todo_list, opts))
+                                       res = -1; /* message was printed */
+                               /* `current` will be incremented below */
+                               todo_list->current = -1;
+                       }
                } else if (!is_noop(item->command))
                        return error(_("unknown command %d"), item->command);
 
@@ -2047,10 +2107,10 @@ 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);
@@ -2058,17 +2118,18 @@ 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;
                        }
+                       strbuf_reset(&buf);
                        if (!read_oneliner(&buf, rebase_path_onto(), 0)) {
                                res = error(_("could not read 'onto'"));
                                goto cleanup_head_ref;
                        }
                        msg = reflog_message(opts, "finish", "%s onto %s",
                                head_ref.buf, buf.buf);
-                       if (update_ref(msg, head_ref.buf, head, orig,
+                       if (update_ref(msg, head_ref.buf, head.hash, orig.hash,
                                        REF_NODEREF, UPDATE_REFS_MSG_ON_ERR)) {
                                res = error(_("could not update %s"),
                                        head_ref.buf);
@@ -2096,10 +2157,10 @@ 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)) {
-                               diff_tree_sha1(orig.hash, head.hash,
-                                              "", &log_tree_opt.diffopt);
+                           !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);
                        }
                }
@@ -2158,12 +2219,12 @@ static int continue_single_pick(void)
 
 static int commit_staged_changes(struct replay_opts *opts)
 {
-       int amend = 0;
+       unsigned int flags = ALLOW_EMPTY | EDIT_MSG;
 
        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");
+               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"));
@@ -2172,26 +2233,26 @@ 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 "
                                       "--continue' again."));
 
                strbuf_release(&rev);
-               amend = 1;
+               flags |= AMEND_MSG;
        }
 
-       if (run_git_commit(rebase_path_message(), opts, 1, 1, amend, 0))
+       if (run_git_commit(rebase_path_message(), opts, flags))
                return error(_("could not commit staged changes."));
        unlink(rebase_path_amend());
        return 0;
@@ -2233,7 +2294,7 @@ 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);
        }
@@ -2254,7 +2315,7 @@ static int single_pick(struct commit *cmit, struct replay_opts *opts)
 int sequencer_pick_revisions(struct replay_opts *opts)
 {
        struct todo_list todo_list = TODO_LIST_INIT;
-       unsigned char sha1[20];
+       struct object_id oid;
        int i, res;
 
        assert(opts->revs);
@@ -2262,16 +2323,16 @@ int sequencer_pick_revisions(struct replay_opts *opts)
                return -1;
 
        for (i = 0; i < opts->revs->pending.nr; i++) {
-               unsigned char sha1[20];
+               struct object_id oid;
                const char *name = opts->revs->pending.objects[i].name;
 
                /* This happens when using --stdin. */
                if (!strlen(name))
                        continue;
 
-               if (!get_sha1(name, sha1)) {
-                       if (!lookup_commit_reference_gently(sha1, 1)) {
-                               enum object_type type = sha1_object_info(sha1, NULL);
+               if (!get_oid(name, &oid)) {
+                       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));
                        }
@@ -2308,9 +2369,9 @@ int sequencer_pick_revisions(struct replay_opts *opts)
        if (walk_revs_populate_todo(&todo_list, opts) ||
                        create_seq_dir() < 0)
                return -1;
-       if (get_sha1("HEAD", sha1) && (opts->action == REPLAY_REVERT))
+       if (get_oid("HEAD", &oid) && (opts->action == REPLAY_REVERT))
                return error(_("can't revert as initial commit"));
-       if (save_head(sha1_to_hex(sha1)))
+       if (save_head(oid_to_hex(&oid)))
                return -1;
        if (save_opts(opts))
                return -1;
@@ -2331,6 +2392,9 @@ void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
                                getenv("GIT_COMMITTER_EMAIL")));
        strbuf_addch(&sob, '\n');
 
+       if (!ignore_footer)
+               strbuf_complete_line(msgbuf);
+
        /*
         * If the whole message buffer is equal to the sob, pretend that we
         * found a conforming footer with a matching sob
@@ -2351,13 +2415,6 @@ void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
                         * the title and body to be filled in by the user.
                         */
                        append_newlines = "\n\n";
-               } else if (msgbuf->buf[len - 1] != '\n') {
-                       /*
-                        * Incomplete line.  Complete the line and add a
-                        * blank one so that there is an empty line between
-                        * the message body and the sob.
-                        */
-                       append_newlines = "\n\n";
                } else if (len == 1) {
                        /*
                         * Buffer contains a single newline.  Add another
@@ -2384,3 +2441,533 @@ void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
 
        strbuf_release(&sob);
 }
+
+int sequencer_make_script(int keep_empty, FILE *out,
+               int argc, const char **argv)
+{
+       char *format = NULL;
+       struct pretty_print_context pp = {0};
+       struct strbuf buf = STRBUF_INIT;
+       struct rev_info revs;
+       struct commit *commit;
+
+       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, "pick %s ", 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;
+}
+
+
+int transform_todo_ids(int shorten_ids)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       int fd, res, i;
+       FILE *out;
+
+       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);
+
+       res = parse_insn_buffer(todo_list.buf.buf, &todo_list);
+       if (res) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       out = fopen(todo_file, "w");
+       if (!out) {
+               todo_list_release(&todo_list);
+               return error(_("unable to open '%s' for writing"), todo_file);
+       }
+       for (i = 0; i < todo_list.nr; i++) {
+               struct todo_item *item = todo_list.items + i;
+               int bol = item->offset_in_buf;
+               const char *p = todo_list.buf.buf + bol;
+               int eol = i + 1 < todo_list.nr ?
+                       todo_list.items[i + 1].offset_in_buf :
+                       todo_list.buf.len;
+
+               if (item->command >= TODO_EXEC && item->command != TODO_DROP)
+                       fwrite(p, eol - bol, 1, out);
+               else {
+                       const char *id = shorten_ids ?
+                               short_commit_name(item->commit) :
+                               oid_to_hex(&item->commit->object.oid);
+                       int len;
+
+                       p += strspn(p, " \t"); /* left-trim command */
+                       len = strcspn(p, " \t"); /* length of command */
+
+                       fprintf(out, "%.*s %s %.*s\n",
+                               len, p, id, item->arg_len, item->arg);
+               }
+       }
+       fclose(out);
+       todo_list_release(&todo_list);
+       return 0;
+}
+
+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, fd, i;
+
+       strbuf_addstr(&todo_file, rebase_path_todo());
+       fd = open(todo_file.buf, O_RDONLY);
+       if (fd < 0) {
+               res = error_errno(_("could not open '%s'"), todo_file.buf);
+               goto leave_check;
+       }
+       if (strbuf_read(&todo_list.buf, fd, 0) < 0) {
+               close(fd);
+               res = error(_("could not read '%s'."), todo_file.buf);
+               goto leave_check;
+       }
+       close(fd);
+       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");
+       fd = open(todo_file.buf, O_RDONLY);
+       if (fd < 0) {
+               res = error_errno(_("could not open '%s'"), todo_file.buf);
+               goto leave_check;
+       }
+       if (strbuf_read(&todo_list.buf, fd, 0) < 0) {
+               close(fd);
+               res = error(_("could not read '%s'."), todo_file.buf);
+               goto leave_check;
+       }
+       close(fd);
+       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;
+}
+
+/* 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);
+
+       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 (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);
+
+               fd = open(rebase_path_todo(), O_WRONLY, 0666);
+               if (fd < 0) {
+                       error_errno(_("could not open '%s' for writing"),
+                                   rebase_path_todo());
+                       todo_list_release(&todo_list);
+                       return -1;
+               }
+               if (write_in_full(fd, todo_list.buf.buf + offset,
+                               todo_list.buf.len - offset) < 0) {
+                       error_errno(_("could not write to '%s'"),
+                                   rebase_path_todo());
+                       close(fd);
+                       todo_list_release(&todo_list);
+                       return -1;
+               }
+               if (ftruncate(fd, todo_list.buf.len - offset) < 0) {
+                       error_errno(_("could not truncate '%s'"),
+                                   rebase_path_todo());
+                       todo_list_release(&todo_list);
+                       close(fd);
+                       return -1;
+               }
+               close(fd);
+
+               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, fd, i;
+       char **subjects;
+
+       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 (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];
+                       }
+               }
+
+               fd = open(todo_file, O_WRONLY);
+               if (fd < 0)
+                       res = error_errno(_("could not open '%s'"), todo_file);
+               else if (write(fd, buf.buf, buf.len) < 0)
+                       res = error_errno(_("could not write to '%s'"), todo_file);
+               else if (ftruncate(fd, buf.len) < 0)
+                       res = error_errno(_("could not truncate '%s'"),
+                                          todo_file);
+               close(fd);
+               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;
+}