repack: add delta-islands support
[gitweb.git] / sequencer.c
index 90c8218aa9a45567cdedcca2b7de4a947117fcc3..31038472fdc0f13e820c43b32cf2e1448b54a543 100644 (file)
@@ -2,6 +2,7 @@
 #include "config.h"
 #include "lockfile.h"
 #include "dir.h"
+#include "object-store.h"
 #include "object.h"
 #include "commit.h"
 #include "sequencer.h"
@@ -27,6 +28,8 @@
 #include "worktree.h"
 #include "oidmap.h"
 #include "oidset.h"
+#include "commit-slab.h"
+#include "alias.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
@@ -60,12 +63,12 @@ static GIT_PATH_FUNC(rebase_path_done, "rebase-merge/done")
  * The file to keep track of how many commands were already processed (e.g.
  * for the prompt).
  */
-static GIT_PATH_FUNC(rebase_path_msgnum, "rebase-merge/msgnum");
+static GIT_PATH_FUNC(rebase_path_msgnum, "rebase-merge/msgnum")
 /*
  * The file to keep track of how many commands are to be processed in total
  * (e.g. for the prompt).
  */
-static GIT_PATH_FUNC(rebase_path_msgtotal, "rebase-merge/end");
+static GIT_PATH_FUNC(rebase_path_msgtotal, "rebase-merge/end")
 /*
  * The commit message that is planned to be used for any changes that
  * need to be committed following a user interaction.
@@ -78,13 +81,6 @@ static GIT_PATH_FUNC(rebase_path_message, "rebase-merge/message")
  * previous commit and from the first squash/fixup commit are written
  * to it. The commit message for each subsequent squash/fixup commit
  * is appended to the file as it is processed.
- *
- * The first line of the file is of the form
- *     # This is a combination of $count commits.
- * where $count is the number of commits whose messages have been
- * written to the file so far (including the initial "pick" commit).
- * Each time that a commit message is processed, this line is read and
- * updated. It is deleted just before the combined commit is made.
  */
 static GIT_PATH_FUNC(rebase_path_squash_msg, "rebase-merge/message-squash")
 /*
@@ -95,6 +91,11 @@ static GIT_PATH_FUNC(rebase_path_squash_msg, "rebase-merge/message-squash")
  * commit without opening the editor.)
  */
 static GIT_PATH_FUNC(rebase_path_fixup_msg, "rebase-merge/message-fixup")
+/*
+ * This file contains the list fixup/squash commands that have been
+ * accumulated into message-fixup or message-squash so far.
+ */
+static GIT_PATH_FUNC(rebase_path_current_fixups, "rebase-merge/current-fixups")
 /*
  * A script to set the GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, and
  * GIT_AUTHOR_DATE that will be used for the commit that is currently
@@ -125,6 +126,12 @@ static GIT_PATH_FUNC(rebase_path_rewritten_list, "rebase-merge/rewritten-list")
 static GIT_PATH_FUNC(rebase_path_rewritten_pending,
        "rebase-merge/rewritten-pending")
 
+/*
+ * The path of the file containig the OID of the "squash onto" commit, i.e.
+ * the dummy commit used for `reset [new root]`.
+ */
+static GIT_PATH_FUNC(rebase_path_squash_onto, "rebase-merge/squash-onto")
+
 /*
  * The path of the file listing refs that need to be deleted after the rebase
  * finishes. This is used by the `label` command to record the need for cleanup.
@@ -170,6 +177,7 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
                        warning(_("invalid commit message cleanup mode '%s'"),
                                  s);
 
+               free((char *)s);
                return status;
        }
 
@@ -279,6 +287,7 @@ int sequencer_remove_state(struct replay_opts *opts)
        for (i = 0; i < opts->xopts_nr; i++)
                free(opts->xopts[i]);
        free(opts->xopts);
+       strbuf_release(&opts->current_fixups);
 
        strbuf_reset(&buf);
        strbuf_addstr(&buf, get_dir(opts));
@@ -349,7 +358,7 @@ static void print_advice(int show_hint, struct replay_opts *opts)
                 * (typically rebase --interactive) wants to take care
                 * of the commit itself so remove CHERRY_PICK_HEAD
                 */
-               unlink(git_path_cherry_pick_head());
+               unlink(git_path_cherry_pick_head(the_repository));
                return;
        }
 
@@ -424,7 +433,7 @@ static int read_oneliner(struct strbuf *buf,
 
 static struct tree *empty_tree(void)
 {
-       return lookup_tree(the_hash_algo->empty_tree);
+       return lookup_tree(the_repository, the_repository->hash_algo->empty_tree);
 }
 
 static int error_dirty_index(struct replay_opts *opts)
@@ -470,7 +479,8 @@ static int fast_forward_to(const struct object_id *to, const struct object_id *f
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
            ref_transaction_update(transaction, "HEAD",
-                                  to, unborn ? &null_oid : from,
+                                  to, unborn && !is_rebase_i(opts) ?
+                                  &null_oid : from,
                                   0, sb.buf, &err) ||
            ref_transaction_commit(transaction, &err)) {
                ref_transaction_free(transaction);
@@ -529,8 +539,8 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
        o.show_rename_progress = 1;
 
        head_tree = parse_tree_indirect(head);
-       next_tree = next ? next->tree : empty_tree();
-       base_tree = base ? base->tree : empty_tree();
+       next_tree = next ? get_commit_tree(next) : empty_tree();
+       base_tree = base ? get_commit_tree(base) : empty_tree();
 
        for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
                parse_merge_opt(&o, *xopt);
@@ -584,7 +594,7 @@ static int is_index_unchanged(void)
        if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
                return error(_("could not resolve HEAD commit"));
 
-       head_commit = lookup_commit(&head_oid);
+       head_commit = lookup_commit(the_repository, &head_oid);
 
        /*
         * If head_commit is NULL, check_commit, called from
@@ -600,7 +610,7 @@ static int is_index_unchanged(void)
        if (!(cache_tree_oid = get_cache_tree_oid()))
                return -1;
 
-       return !oidcmp(cache_tree_oid, &head_commit->tree->object.oid);
+       return !oidcmp(cache_tree_oid, get_commit_tree_oid(head_commit));
 }
 
 static int write_author_script(const char *message)
@@ -692,6 +702,52 @@ static char *get_author(const char *message)
        return NULL;
 }
 
+/* Read author-script and return an ident line (author <email> timestamp) */
+static const char *read_author_ident(struct strbuf *buf)
+{
+       const char *keys[] = {
+               "GIT_AUTHOR_NAME=", "GIT_AUTHOR_EMAIL=", "GIT_AUTHOR_DATE="
+       };
+       char *in, *out, *eol;
+       int i = 0, len;
+
+       if (strbuf_read_file(buf, rebase_path_author_script(), 256) <= 0)
+               return NULL;
+
+       /* dequote values and construct ident line in-place */
+       for (in = out = buf->buf; i < 3 && in - buf->buf < buf->len; i++) {
+               if (!skip_prefix(in, keys[i], (const char **)&in)) {
+                       warning("could not parse '%s' (looking for '%s'",
+                               rebase_path_author_script(), keys[i]);
+                       return NULL;
+               }
+
+               eol = strchrnul(in, '\n');
+               *eol = '\0';
+               sq_dequote(in);
+               len = strlen(in);
+
+               if (i > 0) /* separate values by spaces */
+                       *(out++) = ' ';
+               if (i == 1) /* email needs to be surrounded by <...> */
+                       *(out++) = '<';
+               memmove(out, in, len);
+               out += len;
+               if (i == 1) /* email needs to be surrounded by <...> */
+                       *(out++) = '>';
+               in = eol + 1;
+       }
+
+       if (i < 3) {
+               warning("could not parse '%s' (looking for '%s')",
+                       rebase_path_author_script(), keys[i]);
+               return NULL;
+       }
+
+       buf->len = out - buf->buf;
+       return buf->buf;
+}
+
 static const char staged_changes_advice[] =
 N_("you have staged changes in your working tree\n"
 "If these changes are meant to be squashed into the previous commit, run:\n"
@@ -711,6 +767,7 @@ N_("you have staged changes in your working tree\n"
 #define AMEND_MSG   (1<<2)
 #define CLEANUP_MSG (1<<3)
 #define VERIFY_MSG  (1<<4)
+#define CREATE_ROOT_COMMIT (1<<5)
 
 /*
  * If we are cherry-pick, and if the merge did not result in
@@ -730,6 +787,40 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
        struct child_process cmd = CHILD_PROCESS_INIT;
        const char *value;
 
+       if ((flags & CREATE_ROOT_COMMIT) && !(flags & AMEND_MSG)) {
+               struct strbuf msg = STRBUF_INIT, script = STRBUF_INIT;
+               const char *author = is_rebase_i(opts) ?
+                       read_author_ident(&script) : NULL;
+               struct object_id root_commit, *cache_tree_oid;
+               int res = 0;
+
+               if (!defmsg)
+                       BUG("root commit without message");
+
+               if (!(cache_tree_oid = get_cache_tree_oid()))
+                       res = -1;
+
+               if (!res)
+                       res = strbuf_read_file(&msg, defmsg, 0);
+
+               if (res <= 0)
+                       res = error_errno(_("could not read '%s'"), defmsg);
+               else
+                       res = commit_tree(msg.buf, msg.len, cache_tree_oid,
+                                         NULL, &root_commit, author,
+                                         opts->gpg_sign);
+
+               strbuf_release(&msg);
+               strbuf_release(&script);
+               if (!res) {
+                       update_ref(NULL, "CHERRY_PICK_HEAD", &root_commit, NULL,
+                                  REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR);
+                       res = update_ref(NULL, "HEAD", &root_commit, NULL, 0,
+                                        UPDATE_REFS_MSG_ON_ERR);
+               }
+               return res < 0 ? error(_("writing root commit")) : 0;
+       }
+
        cmd.git_cmd = 1;
 
        if (is_rebase_i(opts)) {
@@ -756,6 +847,8 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
                argv_array_pushf(&cmd.args, "-S%s", opts->gpg_sign);
        if (defmsg)
                argv_array_pushl(&cmd.args, "-F", defmsg, NULL);
+       else if (!(flags & EDIT_MSG))
+               argv_array_pushl(&cmd.args, "-C", "HEAD", NULL);
        if ((flags & CLEANUP_MSG))
                argv_array_push(&cmd.args, "--cleanup=strip");
        if ((flags & EDIT_MSG))
@@ -1008,7 +1101,7 @@ void print_commit_summary(const char *prefix, const struct object_id *oid,
        struct strbuf author_ident = STRBUF_INIT;
        struct strbuf committer_ident = STRBUF_INIT;
 
-       commit = lookup_commit(oid);
+       commit = lookup_commit(the_repository, oid);
        if (!commit)
                die(_("couldn't look up newly created commit"));
        if (parse_commit(commit))
@@ -1083,7 +1176,7 @@ static int parse_head(struct commit **head)
        if (get_oid("HEAD", &oid)) {
                current_head = NULL;
        } else {
-               current_head = lookup_commit_reference(&oid);
+               current_head = lookup_commit_reference(the_repository, &oid);
                if (!current_head)
                        return error(_("could not parse HEAD"));
                if (oidcmp(&oid, &current_head->object.oid)) {
@@ -1157,8 +1250,8 @@ static int try_to_commit(struct strbuf *msg, const char *author,
        }
 
        if (!(flags & ALLOW_EMPTY) && !oidcmp(current_head ?
-                                             &current_head->tree->object.oid :
-                                             &empty_tree_oid, &tree)) {
+                                             get_commit_tree_oid(current_head) :
+                                             the_hash_algo->empty_tree, &tree)) {
                res = 1; /* run 'git commit' to display error message */
                goto out;
        }
@@ -1187,6 +1280,8 @@ static int try_to_commit(struct strbuf *msg, const char *author,
                goto out;
        }
 
+       reset_ident_date();
+
        if (commit_tree_extended(msg->buf, msg->len, &tree, parents,
                                 oid, author, opts->gpg_sign, extra)) {
                res = error(_("failed to write commit object"));
@@ -1216,7 +1311,8 @@ static int do_commit(const char *msg_file, const char *author,
 {
        int res = 1;
 
-       if (!(flags & EDIT_MSG) && !(flags & VERIFY_MSG)) {
+       if (!(flags & EDIT_MSG) && !(flags & VERIFY_MSG) &&
+           !(flags & CREATE_ROOT_COMMIT)) {
                struct object_id oid;
                struct strbuf sb = STRBUF_INIT;
 
@@ -1229,8 +1325,8 @@ static int do_commit(const char *msg_file, const char *author,
                                    &oid);
                strbuf_release(&sb);
                if (!res) {
-                       unlink(git_path_cherry_pick_head());
-                       unlink(git_path_merge_msg());
+                       unlink(git_path_cherry_pick_head(the_repository));
+                       unlink(git_path_merge_msg(the_repository));
                        if (!is_rebase_i(opts))
                                print_commit_summary(NULL, &oid,
                                                SUMMARY_SHOW_AUTHOR_DATE);
@@ -1255,12 +1351,12 @@ static int is_original_commit_empty(struct commit *commit)
                if (parse_commit(parent))
                        return error(_("could not parse parent commit %s"),
                                oid_to_hex(&parent->object.oid));
-               ptree_oid = &parent->tree->object.oid;
+               ptree_oid = get_commit_tree_oid(parent);
        } else {
                ptree_oid = the_hash_algo->empty_tree; /* commit is root */
        }
 
-       return !oidcmp(ptree_oid, &commit->tree->object.oid);
+       return !oidcmp(ptree_oid, get_commit_tree_oid(commit));
 }
 
 /*
@@ -1369,38 +1465,43 @@ static int is_fixup(enum todo_command command)
        return command == TODO_FIXUP || command == TODO_SQUASH;
 }
 
+/* Does this command create a (non-merge) commit? */
+static int is_pick_or_similar(enum todo_command command)
+{
+       switch (command) {
+       case TODO_PICK:
+       case TODO_REVERT:
+       case TODO_EDIT:
+       case TODO_REWORD:
+       case TODO_FIXUP:
+       case TODO_SQUASH:
+               return 1;
+       default:
+               return 0;
+       }
+}
+
 static int update_squash_messages(enum todo_command command,
                struct commit *commit, struct replay_opts *opts)
 {
        struct strbuf buf = STRBUF_INIT;
-       int count, res;
+       int res;
        const char *message, *body;
 
-       if (file_exists(rebase_path_squash_msg())) {
+       if (opts->current_fixup_count > 0) {
                struct strbuf header = STRBUF_INIT;
-               char *eol, *p;
+               char *eol;
 
-               if (strbuf_read_file(&buf, rebase_path_squash_msg(), 2048) <= 0)
+               if (strbuf_read_file(&buf, rebase_path_squash_msg(), 9) <= 0)
                        return error(_("could not read '%s'"),
                                rebase_path_squash_msg());
 
-               p = buf.buf + 1;
-               eol = strchrnul(buf.buf, '\n');
-               if (buf.buf[0] != comment_line_char ||
-                   (p += strcspn(p, "0123456789\n")) == eol)
-                       return error(_("unexpected 1st line of squash message:"
-                                      "\n\n\t%.*s"),
-                                    (int)(eol - buf.buf), buf.buf);
-               count = strtol(p, NULL, 10);
-
-               if (count < 1)
-                       return error(_("invalid 1st line of squash message:\n"
-                                      "\n\t%.*s"),
-                                    (int)(eol - buf.buf), buf.buf);
+               eol = buf.buf[0] != comment_line_char ?
+                       buf.buf : strchrnul(buf.buf, '\n');
 
                strbuf_addf(&header, "%c ", comment_line_char);
-               strbuf_addf(&header,
-                           _("This is a combination of %d commits."), ++count);
+               strbuf_addf(&header, _("This is a combination of %d commits."),
+                           opts->current_fixup_count + 2);
                strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
                strbuf_release(&header);
        } else {
@@ -1410,7 +1511,7 @@ static int update_squash_messages(enum todo_command command,
 
                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(the_repository, &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"));
@@ -1423,10 +1524,8 @@ static int update_squash_messages(enum todo_command command,
                                     rebase_path_fixup_msg());
                }
 
-               count = 2;
                strbuf_addf(&buf, "%c ", comment_line_char);
-               strbuf_addf(&buf, _("This is a combination of %d commits."),
-                           count);
+               strbuf_addf(&buf, _("This is a combination of %d commits."), 2);
                strbuf_addf(&buf, "\n%c ", comment_line_char);
                strbuf_addstr(&buf, _("This is the 1st commit message:"));
                strbuf_addstr(&buf, "\n\n");
@@ -1443,13 +1542,14 @@ static int update_squash_messages(enum todo_command command,
        if (command == TODO_SQUASH) {
                unlink(rebase_path_fixup_msg());
                strbuf_addf(&buf, "\n%c ", comment_line_char);
-               strbuf_addf(&buf, _("This is the commit message #%d:"), count);
+               strbuf_addf(&buf, _("This is the commit message #%d:"),
+                           ++opts->current_fixup_count);
                strbuf_addstr(&buf, "\n\n");
                strbuf_addstr(&buf, body);
        } else if (command == TODO_FIXUP) {
                strbuf_addf(&buf, "\n%c ", comment_line_char);
                strbuf_addf(&buf, _("The commit message #%d will be skipped:"),
-                           count);
+                           ++opts->current_fixup_count);
                strbuf_addstr(&buf, "\n\n");
                strbuf_add_commented_lines(&buf, body, strlen(body));
        } else
@@ -1458,6 +1558,17 @@ static int update_squash_messages(enum todo_command command,
 
        res = write_message(buf.buf, buf.len, rebase_path_squash_msg(), 0);
        strbuf_release(&buf);
+
+       if (!res) {
+               strbuf_addf(&opts->current_fixups, "%s%s %s",
+                           opts->current_fixups.len ? "\n" : "",
+                           command_to_string(command),
+                           oid_to_hex(&commit->object.oid));
+               res = write_message(opts->current_fixups.buf,
+                                   opts->current_fixups.len,
+                                   rebase_path_current_fixups(), 0);
+       }
+
        return res;
 }
 
@@ -1503,7 +1614,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                struct replay_opts *opts, int final_fixup)
 {
        unsigned int flags = opts->edit ? EDIT_MSG : 0;
-       const char *msg_file = opts->edit ? NULL : git_path_merge_msg();
+       const char *msg_file = opts->edit ? NULL : git_path_merge_msg(the_repository);
        struct object_id head;
        struct commit *base, *next, *parent;
        const char *base_label, *next_label;
@@ -1523,9 +1634,16 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        return error(_("your index file is unmerged."));
        } else {
                unborn = get_oid("HEAD", &head);
-               if (unborn)
+               /* Do we want to generate a root commit? */
+               if (is_pick_or_similar(command) && opts->have_squash_onto &&
+                   !oidcmp(&head, &opts->squash_onto)) {
+                       if (is_fixup(command))
+                               return error(_("cannot fixup root commit"));
+                       flags |= CREATE_ROOT_COMMIT;
+                       unborn = 1;
+               } else if (unborn)
                        oidcpy(&head, the_hash_algo->empty_tree);
-               if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD",
+               if (index_differs_from(unborn ? empty_tree_oid_hex() : "HEAD",
                                       NULL, 0))
                        return error_dirty_index(opts);
        }
@@ -1638,12 +1756,12 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                        flags |= CLEANUP_MSG;
                        msg_file = rebase_path_fixup_msg();
                } else {
-                       const char *dest = git_path_squash_msg();
+                       const char *dest = git_path_squash_msg(the_repository);
                        unlink(dest);
                        if (copy_file(dest, rebase_path_squash_msg(), 0666))
                                return error(_("could not rename '%s' to '%s'"),
                                             rebase_path_squash_msg(), dest);
-                       unlink(git_path_merge_msg());
+                       unlink(git_path_merge_msg(the_repository));
                        msg_file = dest;
                        flags |= EDIT_MSG;
                }
@@ -1658,15 +1776,16 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
                res = do_recursive_merge(base, next, base_label, next_label,
                                         &head, &msgbuf, opts);
                if (res < 0)
-                       return res;
+                       goto leave;
+
                res |= write_message(msgbuf.buf, msgbuf.len,
-                                    git_path_merge_msg(), 0);
+                                    git_path_merge_msg(the_repository), 0);
        } else {
                struct commit_list *common = NULL;
                struct commit_list *remotes = NULL;
 
                res = write_message(msgbuf.buf, msgbuf.len,
-                                   git_path_merge_msg(), 0);
+                                   git_path_merge_msg(the_repository), 0);
 
                commit_list_insert(base, &common);
                commit_list_insert(next, &remotes);
@@ -1720,6 +1839,9 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
        if (!res && final_fixup) {
                unlink(rebase_path_fixup_msg());
                unlink(rebase_path_squash_msg());
+               unlink(rebase_path_current_fixups());
+               strbuf_reset(&opts->current_fixups);
+               opts->current_fixup_count = 0;
        }
 
 leave:
@@ -1742,8 +1864,6 @@ static int prepare_revs(struct replay_opts *opts)
        if (prepare_revision_walk(opts->revs))
                return error(_("revision walk setup failed"));
 
-       if (!opts->revs->commits)
-               return error(_("empty commit set passed"));
        return 0;
 }
 
@@ -1887,7 +2007,7 @@ 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_oid);
+       item->commit = lookup_commit_reference(the_repository, &commit_oid);
        return !item->commit;
 }
 
@@ -2085,6 +2205,7 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
 {
        int i;
+       char *strategy_opts_string;
 
        strbuf_reset(buf);
        if (!read_oneliner(buf, rebase_path_strategy(), 0))
@@ -2093,7 +2214,11 @@ static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
        if (!read_oneliner(buf, rebase_path_strategy_opts(), 0))
                return;
 
-       opts->xopts_nr = split_cmdline(buf->buf, (const char ***)&opts->xopts);
+       strategy_opts_string = buf->buf;
+       if (*strategy_opts_string == ' ')
+               strategy_opts_string++;
+       opts->xopts_nr = split_cmdline(strategy_opts_string,
+                                      (const char ***)&opts->xopts);
        for (i = 0; i < opts->xopts_nr; i++) {
                const char *arg = opts->xopts[i];
 
@@ -2136,6 +2261,22 @@ static int read_populate_opts(struct replay_opts *opts)
                read_strategy_opts(opts, &buf);
                strbuf_release(&buf);
 
+               if (read_oneliner(&opts->current_fixups,
+                                 rebase_path_current_fixups(), 1)) {
+                       const char *p = opts->current_fixups.buf;
+                       opts->current_fixup_count = 1;
+                       while ((p = strchr(p, '\n'))) {
+                               opts->current_fixup_count++;
+                               p++;
+                       }
+               }
+
+               if (read_oneliner(&buf, rebase_path_squash_onto(), 0)) {
+                       if (get_oid_hex(buf.buf, &opts->squash_onto) < 0)
+                               return error(_("unusable squash-onto"));
+                       opts->have_squash_onto = 1;
+               }
+
                return 0;
        }
 
@@ -2180,6 +2321,10 @@ static int walk_revs_populate_todo(struct todo_list *todo_list,
                        short_commit_name(commit), subject_len, subject);
                unuse_commit_buffer(commit, commit_buffer);
        }
+
+       if (!todo_list->nr)
+               return error(_("empty commit set passed"));
+
        return 0;
 }
 
@@ -2257,8 +2402,8 @@ static int rollback_single_pick(void)
 {
        struct object_id head_oid;
 
-       if (!file_exists(git_path_cherry_pick_head()) &&
-           !file_exists(git_path_revert_head()))
+       if (!file_exists(git_path_cherry_pick_head(the_repository)) &&
+           !file_exists(git_path_revert_head(the_repository)))
                return error(_("no cherry-pick or revert in progress"));
        if (read_ref_full("HEAD", 0, &head_oid, NULL))
                return error(_("cannot resolve HEAD"));
@@ -2480,14 +2625,14 @@ static int error_with_patch(struct commit *commit,
 static int error_failed_squash(struct commit *commit,
        struct replay_opts *opts, int subject_len, const char *subject)
 {
-       if (rename(rebase_path_squash_msg(), rebase_path_message()))
-               return error(_("could not rename '%s' to '%s'"),
+       if (copy_file(rebase_path_message(), rebase_path_squash_msg(), 0666))
+               return error(_("could not copy '%s' to '%s'"),
                        rebase_path_squash_msg(), rebase_path_message());
-       unlink(rebase_path_fixup_msg());
-       unlink(git_path_merge_msg());
-       if (copy_file(git_path_merge_msg(), rebase_path_message(), 0666))
+       unlink(git_path_merge_msg(the_repository));
+       if (copy_file(git_path_merge_msg(the_repository), rebase_path_message(), 0666))
                return error(_("could not copy '%s' to '%s'"),
-                            rebase_path_message(), git_path_merge_msg());
+                            rebase_path_message(),
+                            git_path_merge_msg(the_repository));
        return error_with_patch(commit, subject, subject_len, opts, 1, 0);
 }
 
@@ -2500,6 +2645,8 @@ static int do_exec(const char *command_line)
        fprintf(stderr, "Executing: %s\n", command_line);
        child_argv[0] = command_line;
        argv_array_pushf(&child_env, "GIT_DIR=%s", absolute_path(get_git_dir()));
+       argv_array_pushf(&child_env, "GIT_WORK_TREE=%s",
+                        absolute_path(get_git_work_tree()));
        status = run_command_v_opt_cd_env(child_argv, RUN_USING_SHELL, NULL,
                                          child_env.argv);
 
@@ -2575,7 +2722,7 @@ static int safe_append(const char *filename, const char *fmt, ...)
 
 static int do_label(const char *name, int len)
 {
-       struct ref_store *refs = get_main_ref_store();
+       struct ref_store *refs = get_main_ref_store(the_repository);
        struct ref_transaction *transaction;
        struct strbuf ref_name = STRBUF_INIT, err = STRBUF_INIT;
        struct strbuf msg = STRBUF_INIT;
@@ -2629,18 +2776,34 @@ static int do_reset(const char *name, int len, struct replay_opts *opts)
        if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
                return -1;
 
-       /* Determine the length of the label */
-       for (i = 0; i < len; i++)
-               if (isspace(name[i]))
-                       len = i;
-
-       strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
-       if (get_oid(ref_name.buf, &oid) &&
-           get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
-               error(_("could not read '%s'"), ref_name.buf);
-               rollback_lock_file(&lock);
-               strbuf_release(&ref_name);
-               return -1;
+       if (len == 10 && !strncmp("[new root]", name, len)) {
+               if (!opts->have_squash_onto) {
+                       const char *hex;
+                       if (commit_tree("", 0, the_hash_algo->empty_tree,
+                                       NULL, &opts->squash_onto,
+                                       NULL, NULL))
+                               return error(_("writing fake root commit"));
+                       opts->have_squash_onto = 1;
+                       hex = oid_to_hex(&opts->squash_onto);
+                       if (write_message(hex, strlen(hex),
+                                         rebase_path_squash_onto(), 0))
+                               return error(_("writing squash-onto"));
+               }
+               oidcpy(&oid, &opts->squash_onto);
+       } else {
+               /* Determine the length of the label */
+               for (i = 0; i < len; i++)
+                       if (isspace(name[i]))
+                               len = i;
+
+               strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
+               if (get_oid(ref_name.buf, &oid) &&
+                   get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
+                       error(_("could not read '%s'"), ref_name.buf);
+                       rollback_lock_file(&lock);
+                       strbuf_release(&ref_name);
+                       return -1;
+               }
        }
 
        memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
@@ -2689,6 +2852,26 @@ static int do_reset(const char *name, int len, struct replay_opts *opts)
        return ret;
 }
 
+static struct commit *lookup_label(const char *label, int len,
+                                  struct strbuf *buf)
+{
+       struct commit *commit;
+
+       strbuf_reset(buf);
+       strbuf_addf(buf, "refs/rewritten/%.*s", len, label);
+       commit = lookup_commit_reference_by_name(buf->buf);
+       if (!commit) {
+               /* fall back to non-rewritten ref or commit */
+               strbuf_splice(buf, 0, strlen("refs/rewritten/"), "", 0);
+               commit = lookup_commit_reference_by_name(buf->buf);
+       }
+
+       if (!commit)
+               error(_("could not resolve '%s'"), buf->buf);
+
+       return commit;
+}
+
 static int do_merge(struct commit *commit, const char *arg, int arg_len,
                    int flags, struct replay_opts *opts)
 {
@@ -2697,8 +2880,9 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
        struct strbuf ref_name = STRBUF_INIT;
        struct commit *head_commit, *merge_commit, *i;
        struct commit_list *bases, *j, *reversed = NULL;
+       struct commit_list *to_merge = NULL, **tail = &to_merge;
        struct merge_options o;
-       int merge_arg_len, oneline_offset, can_fast_forward, ret;
+       int merge_arg_len, oneline_offset, can_fast_forward, ret, k;
        static struct lock_file lock;
        const char *p;
 
@@ -2713,26 +2897,51 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
                goto leave_merge;
        }
 
-       oneline_offset = arg_len;
-       merge_arg_len = strcspn(arg, " \t\n");
-       p = arg + merge_arg_len;
-       p += strspn(p, " \t\n");
-       if (*p == '#' && (!p[1] || isspace(p[1]))) {
-               p += 1 + strspn(p + 1, " \t\n");
-               oneline_offset = p - arg;
-       } else if (p - arg < arg_len)
-               BUG("octopus merges are not supported yet: '%s'", p);
+       /*
+        * For octopus merges, the arg starts with the list of revisions to be
+        * merged. The list is optionally followed by '#' and the oneline.
+        */
+       merge_arg_len = oneline_offset = arg_len;
+       for (p = arg; p - arg < arg_len; p += strspn(p, " \t\n")) {
+               if (!*p)
+                       break;
+               if (*p == '#' && (!p[1] || isspace(p[1]))) {
+                       p += 1 + strspn(p + 1, " \t\n");
+                       oneline_offset = p - arg;
+                       break;
+               }
+               k = strcspn(p, " \t\n");
+               if (!k)
+                       continue;
+               merge_commit = lookup_label(p, k, &ref_name);
+               if (!merge_commit) {
+                       ret = error(_("unable to parse '%.*s'"), k, p);
+                       goto leave_merge;
+               }
+               tail = &commit_list_insert(merge_commit, tail)->next;
+               p += k;
+               merge_arg_len = p - arg;
+       }
 
-       strbuf_addf(&ref_name, "refs/rewritten/%.*s", merge_arg_len, arg);
-       merge_commit = lookup_commit_reference_by_name(ref_name.buf);
-       if (!merge_commit) {
-               /* fall back to non-rewritten ref or commit */
-               strbuf_splice(&ref_name, 0, strlen("refs/rewritten/"), "", 0);
-               merge_commit = lookup_commit_reference_by_name(ref_name.buf);
+       if (!to_merge) {
+               ret = error(_("nothing to merge: '%.*s'"), arg_len, arg);
+               goto leave_merge;
        }
 
-       if (!merge_commit) {
-               ret = error(_("could not resolve '%s'"), ref_name.buf);
+       if (opts->have_squash_onto &&
+           !oidcmp(&head_commit->object.oid, &opts->squash_onto)) {
+               /*
+                * When the user tells us to "merge" something into a
+                * "[new root]", let's simply fast-forward to the merge head.
+                */
+               rollback_lock_file(&lock);
+               if (to_merge->next)
+                       ret = error(_("octopus merge cannot be executed on "
+                                     "top of a [new root]"));
+               else
+                       ret = fast_forward_to(&to_merge->item->object.oid,
+                                             &head_commit->object.oid, 0,
+                                             opts);
                goto leave_merge;
        }
 
@@ -2749,11 +2958,11 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
                write_author_script(message);
                find_commit_subject(message, &body);
                len = strlen(body);
-               ret = write_message(body, len, git_path_merge_msg(), 0);
+               ret = write_message(body, len, git_path_merge_msg(the_repository), 0);
                unuse_commit_buffer(commit, message);
                if (ret) {
                        error_errno(_("could not write '%s'"),
-                                   git_path_merge_msg());
+                                   git_path_merge_msg(the_repository));
                        goto leave_merge;
                }
        } else {
@@ -2768,17 +2977,18 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
                        p = arg + oneline_offset;
                        len = arg_len - oneline_offset;
                } else {
-                       strbuf_addf(&buf, "Merge branch '%.*s'",
+                       strbuf_addf(&buf, "Merge %s '%.*s'",
+                                   to_merge->next ? "branches" : "branch",
                                    merge_arg_len, arg);
                        p = buf.buf;
                        len = buf.len;
                }
 
-               ret = write_message(p, len, git_path_merge_msg(), 0);
+               ret = write_message(p, len, git_path_merge_msg(the_repository), 0);
                strbuf_release(&buf);
                if (ret) {
                        error_errno(_("could not write '%s'"),
-                                   git_path_merge_msg());
+                                   git_path_merge_msg(the_repository));
                        goto leave_merge;
                }
        }
@@ -2792,31 +3002,79 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
                        &head_commit->object.oid);
 
        /*
-        * If the merge head is different from the original one, we cannot
+        * If any merge head is different from the original one, we cannot
         * fast-forward.
         */
        if (can_fast_forward) {
-               struct commit_list *second_parent = commit->parents->next;
+               struct commit_list *p = commit->parents->next;
 
-               if (second_parent && !second_parent->next &&
-                   oidcmp(&merge_commit->object.oid,
-                          &second_parent->item->object.oid))
+               for (j = to_merge; j && p; j = j->next, p = p->next)
+                       if (oidcmp(&j->item->object.oid,
+                                  &p->item->object.oid)) {
+                               can_fast_forward = 0;
+                               break;
+                       }
+               /*
+                * If the number of merge heads differs from the original merge
+                * commit, we cannot fast-forward.
+                */
+               if (j || p)
                        can_fast_forward = 0;
        }
 
-       if (can_fast_forward && commit->parents->next &&
-           !commit->parents->next->next &&
-           !oidcmp(&commit->parents->next->item->object.oid,
-                   &merge_commit->object.oid)) {
+       if (can_fast_forward) {
                rollback_lock_file(&lock);
                ret = fast_forward_to(&commit->object.oid,
                                      &head_commit->object.oid, 0, opts);
                goto leave_merge;
        }
 
+       if (to_merge->next) {
+               /* Octopus merge */
+               struct child_process cmd = CHILD_PROCESS_INIT;
+
+               if (read_env_script(&cmd.env_array)) {
+                       const char *gpg_opt = gpg_sign_opt_quoted(opts);
+
+                       ret = error(_(staged_changes_advice), gpg_opt, gpg_opt);
+                       goto leave_merge;
+               }
+
+               cmd.git_cmd = 1;
+               argv_array_push(&cmd.args, "merge");
+               argv_array_push(&cmd.args, "-s");
+               argv_array_push(&cmd.args, "octopus");
+               argv_array_push(&cmd.args, "--no-edit");
+               argv_array_push(&cmd.args, "--no-ff");
+               argv_array_push(&cmd.args, "--no-log");
+               argv_array_push(&cmd.args, "--no-stat");
+               argv_array_push(&cmd.args, "-F");
+               argv_array_push(&cmd.args, git_path_merge_msg(the_repository));
+               if (opts->gpg_sign)
+                       argv_array_push(&cmd.args, opts->gpg_sign);
+
+               /* Add the tips to be merged */
+               for (j = to_merge; j; j = j->next)
+                       argv_array_push(&cmd.args,
+                                       oid_to_hex(&j->item->object.oid));
+
+               strbuf_release(&ref_name);
+               unlink(git_path_cherry_pick_head(the_repository));
+               rollback_lock_file(&lock);
+
+               rollback_lock_file(&lock);
+               ret = run_command(&cmd);
+
+               /* force re-reading of the cache */
+               if (!ret && (discard_cache() < 0 || read_cache() < 0))
+                       ret = error(_("could not read index"));
+               goto leave_merge;
+       }
+
+       merge_commit = to_merge->item;
        write_message(oid_to_hex(&merge_commit->object.oid), GIT_SHA1_HEXSZ,
-                     git_path_merge_head(), 0);
-       write_message("no-ff", 5, git_path_merge_mode(), 0);
+                     git_path_merge_head(the_repository), 0);
+       write_message("no-ff", 5, git_path_merge_mode(the_repository), 0);
 
        bases = get_merge_bases(head_commit, merge_commit);
        if (bases && !oidcmp(&merge_commit->object.oid,
@@ -2870,12 +3128,13 @@ static int do_merge(struct commit *commit, const char *arg, int arg_len,
                 * value (a negative one would indicate that the `merge`
                 * command needs to be rescheduled).
                 */
-               ret = !!run_git_commit(git_path_merge_msg(), opts,
+               ret = !!run_git_commit(git_path_merge_msg(the_repository), opts,
                                     run_commit_flags);
 
 leave_merge:
        strbuf_release(&ref_name);
        rollback_lock_file(&lock);
+       free_commit_list(to_merge);
        return ret;
 }
 
@@ -3053,10 +3312,27 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
                                        intend_to_amend();
                                return error_failed_squash(item->commit, opts,
                                        item->arg_len, item->arg);
-                       } else if (res && is_rebase_i(opts) && item->commit)
+                       } else if (res && is_rebase_i(opts) && item->commit) {
+                               int to_amend = 0;
+                               struct object_id oid;
+
+                               /*
+                                * If we are rewording and have either
+                                * fast-forwarded already, or are about to
+                                * create a new root commit, we want to amend,
+                                * otherwise we do not.
+                                */
+                               if (item->command == TODO_REWORD &&
+                                   !get_oid("HEAD", &oid) &&
+                                   (!oidcmp(&item->commit->object.oid, &oid) ||
+                                    (opts->have_squash_onto &&
+                                     !oidcmp(&opts->squash_onto, &oid))))
+                                       to_amend = 1;
+
                                return res | error_with_patch(item->commit,
-                                       item->arg, item->arg_len, opts, res,
-                                       item->command == TODO_REWORD);
+                                               item->arg, item->arg_len, opts,
+                                               res, to_amend);
+                       }
                } else if (item->command == TODO_EXEC) {
                        char *end_of_arg = (char *)(item->arg + item->arg_len);
                        int saved = *end_of_arg;
@@ -3237,25 +3513,22 @@ static int continue_single_pick(void)
 {
        const char *argv[] = { "commit", NULL };
 
-       if (!file_exists(git_path_cherry_pick_head()) &&
-           !file_exists(git_path_revert_head()))
+       if (!file_exists(git_path_cherry_pick_head(the_repository)) &&
+           !file_exists(git_path_revert_head(the_repository)))
                return error(_("no cherry-pick or revert in progress"));
        return run_command_v_opt(argv, RUN_GIT_CMD);
 }
 
-static int commit_staged_changes(struct replay_opts *opts)
+static int commit_staged_changes(struct replay_opts *opts,
+                                struct todo_list *todo_list)
 {
        unsigned int flags = ALLOW_EMPTY | EDIT_MSG;
+       unsigned int final_fixup = 0, is_clean;
 
        if (has_unstaged_changes(1))
                return error(_("cannot rebase: You have unstaged changes."));
-       if (!has_uncommitted_changes(0)) {
-               const char *cherry_pick_head = git_path_cherry_pick_head();
 
-               if (file_exists(cherry_pick_head) && unlink(cherry_pick_head))
-                       return error(_("could not remove CHERRY_PICK_HEAD"));
-               return 0;
-       }
+       is_clean = !has_uncommitted_changes(0);
 
        if (file_exists(rebase_path_amend())) {
                struct strbuf rev = STRBUF_INIT;
@@ -3268,19 +3541,107 @@ static int commit_staged_changes(struct replay_opts *opts)
                if (get_oid_hex(rev.buf, &to_amend))
                        return error(_("invalid contents: '%s'"),
                                rebase_path_amend());
-               if (oidcmp(&head, &to_amend))
+               if (!is_clean && oidcmp(&head, &to_amend))
                        return error(_("\nYou have uncommitted changes in your "
                                       "working tree. Please, commit them\n"
                                       "first and then run 'git rebase "
                                       "--continue' again."));
+               /*
+                * When skipping a failed fixup/squash, we need to edit the
+                * commit message, the current fixup list and count, and if it
+                * was the last fixup/squash in the chain, we need to clean up
+                * the commit message and if there was a squash, let the user
+                * edit it.
+                */
+               if (is_clean && !oidcmp(&head, &to_amend) &&
+                   opts->current_fixup_count > 0 &&
+                   file_exists(rebase_path_stopped_sha())) {
+                       const char *p = opts->current_fixups.buf;
+                       int len = opts->current_fixups.len;
+
+                       opts->current_fixup_count--;
+                       if (!len)
+                               BUG("Incorrect current_fixups:\n%s", p);
+                       while (len && p[len - 1] != '\n')
+                               len--;
+                       strbuf_setlen(&opts->current_fixups, len);
+                       if (write_message(p, len, rebase_path_current_fixups(),
+                                         0) < 0)
+                               return error(_("could not write file: '%s'"),
+                                            rebase_path_current_fixups());
+
+                       /*
+                        * If a fixup/squash in a fixup/squash chain failed, the
+                        * commit message is already correct, no need to commit
+                        * it again.
+                        *
+                        * Only if it is the final command in the fixup/squash
+                        * chain, and only if the chain is longer than a single
+                        * fixup/squash command (which was just skipped), do we
+                        * actually need to re-commit with a cleaned up commit
+                        * message.
+                        */
+                       if (opts->current_fixup_count > 0 &&
+                           !is_fixup(peek_command(todo_list, 0))) {
+                               final_fixup = 1;
+                               /*
+                                * If there was not a single "squash" in the
+                                * chain, we only need to clean up the commit
+                                * message, no need to bother the user with
+                                * opening the commit message in the editor.
+                                */
+                               if (!starts_with(p, "squash ") &&
+                                   !strstr(p, "\nsquash "))
+                                       flags = (flags & ~EDIT_MSG) | CLEANUP_MSG;
+                       } else if (is_fixup(peek_command(todo_list, 0))) {
+                               /*
+                                * We need to update the squash message to skip
+                                * the latest commit message.
+                                */
+                               struct commit *commit;
+                               const char *path = rebase_path_squash_msg();
+
+                               if (parse_head(&commit) ||
+                                   !(p = get_commit_buffer(commit, NULL)) ||
+                                   write_message(p, strlen(p), path, 0)) {
+                                       unuse_commit_buffer(commit, p);
+                                       return error(_("could not write file: "
+                                                      "'%s'"), path);
+                               }
+                               unuse_commit_buffer(commit, p);
+                       }
+               }
 
                strbuf_release(&rev);
                flags |= AMEND_MSG;
        }
 
-       if (run_git_commit(rebase_path_message(), opts, flags))
+       if (is_clean) {
+               const char *cherry_pick_head = git_path_cherry_pick_head(the_repository);
+
+               if (file_exists(cherry_pick_head) && unlink(cherry_pick_head))
+                       return error(_("could not remove CHERRY_PICK_HEAD"));
+               if (!final_fixup)
+                       return 0;
+       }
+
+       if (run_git_commit(final_fixup ? NULL : rebase_path_message(),
+                          opts, flags))
                return error(_("could not commit staged changes."));
        unlink(rebase_path_amend());
+       if (final_fixup) {
+               unlink(rebase_path_fixup_msg());
+               unlink(rebase_path_squash_msg());
+       }
+       if (opts->current_fixup_count > 0) {
+               /*
+                * Whether final fixup or not, we just cleaned up the commit
+                * message...
+                */
+               unlink(rebase_path_current_fixups());
+               strbuf_reset(&opts->current_fixups);
+               opts->current_fixup_count = 0;
+       }
        return 0;
 }
 
@@ -3292,20 +3653,22 @@ int sequencer_continue(struct replay_opts *opts)
        if (read_and_refresh_cache(opts))
                return -1;
 
+       if (read_populate_opts(opts))
+               return -1;
        if (is_rebase_i(opts)) {
-               if (commit_staged_changes(opts))
+               if ((res = read_populate_todo(&todo_list, opts)))
+                       goto release_todo_list;
+               if (commit_staged_changes(opts, &todo_list))
                        return -1;
        } else if (!file_exists(get_todo_path(opts)))
                return continue_single_pick();
-       if (read_populate_opts(opts))
-               return -1;
-       if ((res = read_populate_todo(&todo_list, opts)))
+       else if ((res = read_populate_todo(&todo_list, opts)))
                goto release_todo_list;
 
        if (!is_rebase_i(opts)) {
                /* Verify that the conflict has been resolved */
-               if (file_exists(git_path_cherry_pick_head()) ||
-                   file_exists(git_path_revert_head())) {
+               if (file_exists(git_path_cherry_pick_head(the_repository)) ||
+                   file_exists(git_path_revert_head(the_repository))) {
                        res = continue_single_pick();
                        if (res)
                                goto release_todo_list;
@@ -3357,8 +3720,9 @@ int sequencer_pick_revisions(struct replay_opts *opts)
                        continue;
 
                if (!get_oid(name, &oid)) {
-                       if (!lookup_commit_reference_gently(&oid, 1)) {
-                               enum object_type type = oid_object_info(&oid,
+                       if (!lookup_commit_reference_gently(the_repository, &oid, 1)) {
+                               enum object_type type = oid_object_info(the_repository,
+                                                                       &oid,
                                                                        NULL);
                                return error(_("%s: can't cherry-pick a %s"),
                                        name, type_name(type));
@@ -3382,8 +3746,10 @@ int sequencer_pick_revisions(struct replay_opts *opts)
                if (prepare_revision_walk(opts->revs))
                        return error(_("revision walk setup failed"));
                cmit = get_revision(opts->revs);
-               if (!cmit || get_revision(opts->revs))
-                       return error("BUG: expected exactly one commit from walk");
+               if (!cmit)
+                       return error(_("empty commit set passed"));
+               if (get_revision(opts->revs))
+                       BUG("unexpected extra commit from walk");
                return single_pick(cmit, opts);
        }
 
@@ -3543,7 +3909,7 @@ static const char *label_oid(struct object_id *oid, const char *label,
                                p[i] = save;
                        }
                }
-       } else if (((len = strlen(label)) == GIT_SHA1_RAWSZ &&
+       } else if (((len = strlen(label)) == the_hash_algo->hexsz &&
                    !get_oid_hex(label, &dummy)) ||
                   (len == 1 && *label == '#') ||
                   hashmap_get_from_hash(&state->labels,
@@ -3625,7 +3991,6 @@ static int make_script_with_merges(struct pretty_print_context *pp,
         */
        while ((commit = get_revision(revs))) {
                struct commit_list *to_merge;
-               int is_octopus;
                const char *p1, *p2;
                struct object_id *oid;
                int is_empty;
@@ -3657,11 +4022,6 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                        continue;
                }
 
-               is_octopus = to_merge && to_merge->next;
-
-               if (is_octopus)
-                       BUG("Octopus merges not yet supported");
-
                /* Create a label */
                strbuf_reset(&label);
                if (skip_prefix(oneline.buf, "Merge ", &p1) &&
@@ -3683,13 +4043,17 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                strbuf_addf(&buf, "%s -C %s",
                            cmd_merge, oid_to_hex(&commit->object.oid));
 
-               /* label the tip of merged branch */
-               oid = &to_merge->item->object.oid;
-               strbuf_addch(&buf, ' ');
+               /* label the tips of merged branches */
+               for (; to_merge; to_merge = to_merge->next) {
+                       oid = &to_merge->item->object.oid;
+                       strbuf_addch(&buf, ' ');
+
+                       if (!oidset_contains(&interesting, oid)) {
+                               strbuf_addstr(&buf, label_oid(oid, NULL,
+                                                             &state));
+                               continue;
+                       }
 
-               if (!oidset_contains(&interesting, oid))
-                       strbuf_addstr(&buf, label_oid(oid, NULL, &state));
-               else {
                        tips_tail = &commit_list_insert(to_merge->item,
                                                        tips_tail)->next;
 
@@ -3742,7 +4106,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                entry = oidmap_get(&state.commit2label, &commit->object.oid);
 
                if (entry)
-                       fprintf(out, "\n# Branch %s\n", entry->string);
+                       fprintf(out, "\n%c Branch %s\n", comment_line_char, entry->string);
                else
                        fprintf(out, "\n");
 
@@ -3757,7 +4121,8 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                }
 
                if (!commit)
-                       fprintf(out, "%s onto\n", cmd_reset);
+                       fprintf(out, "%s %s\n", cmd_reset,
+                               rebase_cousins ? "onto" : "[new root]");
                else {
                        const char *to = NULL;
 
@@ -3988,6 +4353,7 @@ static enum check_level get_missing_commit_check_level(void)
        return CHECK_IGNORE;
 }
 
+define_commit_slab(commit_seen, unsigned char);
 /*
  * Check if the user dropped some commits by mistake
  * Behaviour determined by rebase.missingCommitsCheck.
@@ -4001,6 +4367,9 @@ int check_todo_list(void)
        struct todo_list todo_list = TODO_LIST_INIT;
        struct strbuf missing = STRBUF_INIT;
        int advise_to_edit_todo = 0, res = 0, i;
+       struct commit_seen commit_seen;
+
+       init_commit_seen(&commit_seen);
 
        strbuf_addstr(&todo_file, rebase_path_todo());
        if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
@@ -4017,7 +4386,7 @@ int check_todo_list(void)
        for (i = 0; i < todo_list.nr; i++) {
                struct commit *commit = todo_list.items[i].commit;
                if (commit)
-                       commit->util = (void *)1;
+                       *commit_seen_at(&commit_seen, commit) = 1;
        }
 
        todo_list_release(&todo_list);
@@ -4033,11 +4402,11 @@ int check_todo_list(void)
        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) {
+               if (commit && !*commit_seen_at(&commit_seen, commit)) {
                        strbuf_addf(&missing, " - %s %.*s\n",
                                    short_commit_name(commit),
                                    item->arg_len, item->arg);
-                       commit->util = (void *)1;
+                       *commit_seen_at(&commit_seen, commit) = 1;
                }
        }
 
@@ -4063,6 +4432,7 @@ int check_todo_list(void)
                "The possible behaviours are: ignore, warn, error.\n\n"));
 
 leave_check:
+       clear_commit_seen(&commit_seen);
        strbuf_release(&todo_file);
        todo_list_release(&todo_list);
 
@@ -4183,6 +4553,8 @@ static int subject2item_cmp(const void *fndata,
        return key ? strcmp(a->subject, key) : strcmp(a->subject, b->subject);
 }
 
+define_commit_slab(commit_todo_item, struct todo_item *);
+
 /*
  * Rearrange the todo list that has both "pick commit-id msg" and "pick
  * commit-id fixup!/squash! msg" in it so that the latter is put immediately
@@ -4199,6 +4571,7 @@ int rearrange_squash(void)
        struct hashmap subject2item;
        int res = 0, rearranged = 0, *next, *tail, i;
        char **subjects;
+       struct commit_todo_item commit_todo;
 
        if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
                return -1;
@@ -4207,6 +4580,7 @@ int rearrange_squash(void)
                return -1;
        }
 
+       init_commit_todo_item(&commit_todo);
        /*
         * The hashmap maps onelines to the respective todo list index.
         *
@@ -4237,10 +4611,11 @@ int rearrange_squash(void)
 
                if (is_fixup(item->command)) {
                        todo_list_release(&todo_list);
+                       clear_commit_todo_item(&commit_todo);
                        return error(_("the script was already rearranged."));
                }
 
-               item->commit->util = item;
+               *commit_todo_item_at(&commit_todo, item->commit) = item;
 
                parse_commit(item->commit);
                commit_buffer = get_commit_buffer(item->commit, NULL);
@@ -4267,9 +4642,9 @@ int rearrange_squash(void)
                        else if (!strchr(p, ' ') &&
                                 (commit2 =
                                  lookup_commit_reference_by_name(p)) &&
-                                commit2->util)
+                                *commit_todo_item_at(&commit_todo, commit2))
                                /* found by commit name */
-                               i2 = (struct todo_item *)commit2->util
+                               i2 = *commit_todo_item_at(&commit_todo, commit2)
                                        - todo_list.items;
                        else {
                                /* copy can be a prefix of the commit subject */
@@ -4346,5 +4721,6 @@ int rearrange_squash(void)
        hashmap_free(&subject2item, 1);
        todo_list_release(&todo_list);
 
+       clear_commit_todo_item(&commit_todo);
        return res;
 }