Git 2.23
[gitweb.git] / builtin / rebase.c
index 8a7bf3d468bab612a462e8352b77ac9fd71a8e1e..670096c065f5f5fa8cb57c642cd759111b010988 100644 (file)
@@ -4,6 +4,7 @@
  * Copyright (c) 2018 Pratik Karki
  */
 
+#define USE_THE_INDEX_COMPATIBILITY_MACROS
 #include "builtin.h"
 #include "run-command.h"
 #include "exec-cmd.h"
 #include "diff.h"
 #include "wt-status.h"
 #include "revision.h"
+#include "commit-reach.h"
+#include "rerere.h"
+#include "branch.h"
+#include "sequencer.h"
+#include "rebase-interactive.h"
 
 static char const * const builtin_rebase_usage[] = {
        N_("git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] "
@@ -31,6 +37,8 @@ static char const * const builtin_rebase_usage[] = {
        NULL
 };
 
+static GIT_PATH_FUNC(path_squash_onto, "rebase-merge/squash-onto")
+static GIT_PATH_FUNC(path_interactive, "rebase-merge/interactive")
 static GIT_PATH_FUNC(apply_dir, "rebase-apply")
 static GIT_PATH_FUNC(merge_dir, "rebase-merge")
 
@@ -42,32 +50,6 @@ enum rebase_type {
        REBASE_PRESERVE_MERGES
 };
 
-static int use_builtin_rebase(void)
-{
-       struct child_process cp = CHILD_PROCESS_INIT;
-       struct strbuf out = STRBUF_INIT;
-       int ret;
-
-       argv_array_pushl(&cp.args,
-                        "config", "--bool", "rebase.usebuiltin", NULL);
-       cp.git_cmd = 1;
-       if (capture_command(&cp, &out, 6)) {
-               strbuf_release(&out);
-               return 0;
-       }
-
-       strbuf_trim(&out);
-       ret = !strcmp("true", out.buf);
-       strbuf_release(&out);
-       return ret;
-}
-
-static int apply_autostash(void)
-{
-       warning("TODO");
-       return 0;
-}
-
 struct rebase_options {
        enum rebase_type type;
        const char *state_dir;
@@ -79,7 +61,9 @@ struct rebase_options {
        struct commit *onto;
        const char *onto_name;
        const char *revisions;
+       const char *switch_to;
        int root;
+       struct object_id *squash_onto;
        struct commit *restrict_revision;
        int dont_finish_rebase;
        enum {
@@ -87,16 +71,479 @@ struct rebase_options {
                REBASE_VERBOSE = 1<<1,
                REBASE_DIFFSTAT = 1<<2,
                REBASE_FORCE = 1<<3,
+               REBASE_INTERACTIVE_EXPLICIT = 1<<4,
        } flags;
-       struct strbuf git_am_opt;
+       struct argv_array git_am_opts;
+       const char *action;
+       int signoff;
+       int allow_rerere_autoupdate;
+       int keep_empty;
+       int autosquash;
+       char *gpg_sign_opt;
+       int autostash;
+       char *cmd;
+       int allow_empty_message;
+       int rebase_merges, rebase_cousins;
+       char *strategy, *strategy_opts;
+       struct strbuf git_format_patch_opt;
+       int reschedule_failed_exec;
+       int use_legacy_rebase;
+};
+
+#define REBASE_OPTIONS_INIT {                          \
+               .type = REBASE_UNSPECIFIED,             \
+               .flags = REBASE_NO_QUIET,               \
+               .git_am_opts = ARGV_ARRAY_INIT,         \
+               .git_format_patch_opt = STRBUF_INIT     \
+       }
+
+static struct replay_opts get_replay_opts(const struct rebase_options *opts)
+{
+       struct replay_opts replay = REPLAY_OPTS_INIT;
+
+       replay.action = REPLAY_INTERACTIVE_REBASE;
+       sequencer_init_config(&replay);
+
+       replay.signoff = opts->signoff;
+       replay.allow_ff = !(opts->flags & REBASE_FORCE);
+       if (opts->allow_rerere_autoupdate)
+               replay.allow_rerere_auto = opts->allow_rerere_autoupdate;
+       replay.allow_empty = 1;
+       replay.allow_empty_message = opts->allow_empty_message;
+       replay.verbose = opts->flags & REBASE_VERBOSE;
+       replay.reschedule_failed_exec = opts->reschedule_failed_exec;
+       replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
+       replay.strategy = opts->strategy;
+       if (opts->strategy_opts)
+               parse_strategy_opts(&replay, opts->strategy_opts);
+
+       return replay;
+}
+
+enum action {
+       ACTION_NONE = 0,
+       ACTION_CONTINUE,
+       ACTION_SKIP,
+       ACTION_ABORT,
+       ACTION_QUIT,
+       ACTION_EDIT_TODO,
+       ACTION_SHOW_CURRENT_PATCH,
+       ACTION_SHORTEN_OIDS,
+       ACTION_EXPAND_OIDS,
+       ACTION_CHECK_TODO_LIST,
+       ACTION_REARRANGE_SQUASH,
+       ACTION_ADD_EXEC
+};
+
+static const char *action_names[] = { "undefined",
+                                     "continue",
+                                     "skip",
+                                     "abort",
+                                     "quit",
+                                     "edit_todo",
+                                     "show_current_patch" };
+
+static int add_exec_commands(struct string_list *commands)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       int res;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error_errno(_("could not read '%s'."), todo_file);
+
+       if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
+                                       &todo_list)) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       todo_list_add_exec_commands(&todo_list, commands);
+       res = todo_list_write_to_file(the_repository, &todo_list,
+                                     todo_file, NULL, NULL, -1, 0);
+       todo_list_release(&todo_list);
+
+       if (res)
+               return error_errno(_("could not write '%s'."), todo_file);
+       return 0;
+}
+
+static int rearrange_squash_in_todo_file(void)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       int res = 0;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error_errno(_("could not read '%s'."), todo_file);
+       if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
+                                       &todo_list)) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       res = todo_list_rearrange_squash(&todo_list);
+       if (!res)
+               res = todo_list_write_to_file(the_repository, &todo_list,
+                                             todo_file, NULL, NULL, -1, 0);
+
+       todo_list_release(&todo_list);
+
+       if (res)
+               return error_errno(_("could not write '%s'."), todo_file);
+       return 0;
+}
+
+static int transform_todo_file(unsigned flags)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT;
+       int res;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error_errno(_("could not read '%s'."), todo_file);
+
+       if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
+                                       &todo_list)) {
+               todo_list_release(&todo_list);
+               return error(_("unusable todo list: '%s'"), todo_file);
+       }
+
+       res = todo_list_write_to_file(the_repository, &todo_list, todo_file,
+                                     NULL, NULL, -1, flags);
+       todo_list_release(&todo_list);
+
+       if (res)
+               return error_errno(_("could not write '%s'."), todo_file);
+       return 0;
+}
+
+static int edit_todo_file(unsigned flags)
+{
+       const char *todo_file = rebase_path_todo();
+       struct todo_list todo_list = TODO_LIST_INIT,
+               new_todo = TODO_LIST_INIT;
+       int res = 0;
+
+       if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+               return error_errno(_("could not read '%s'."), todo_file);
+
+       strbuf_stripspace(&todo_list.buf, 1);
+       res = edit_todo_list(the_repository, &todo_list, &new_todo, NULL, NULL, flags);
+       if (!res && todo_list_write_to_file(the_repository, &new_todo, todo_file,
+                                           NULL, NULL, -1, flags & ~(TODO_LIST_SHORTEN_IDS)))
+               res = error_errno(_("could not write '%s'"), todo_file);
+
+       todo_list_release(&todo_list);
+       todo_list_release(&new_todo);
+
+       return res;
+}
+
+static int get_revision_ranges(struct commit *upstream, struct commit *onto,
+                              const char **head_hash,
+                              char **revisions, char **shortrevisions)
+{
+       struct commit *base_rev = upstream ? upstream : onto;
+       const char *shorthead;
+       struct object_id orig_head;
+
+       if (get_oid("HEAD", &orig_head))
+               return error(_("no HEAD?"));
+
+       *head_hash = find_unique_abbrev(&orig_head, GIT_MAX_HEXSZ);
+       *revisions = xstrfmt("%s...%s", oid_to_hex(&base_rev->object.oid),
+                                                  *head_hash);
+
+       shorthead = find_unique_abbrev(&orig_head, DEFAULT_ABBREV);
+
+       if (upstream) {
+               const char *shortrev;
+
+               shortrev = find_unique_abbrev(&base_rev->object.oid,
+                                             DEFAULT_ABBREV);
+
+               *shortrevisions = xstrfmt("%s..%s", shortrev, shorthead);
+       } else
+               *shortrevisions = xstrdup(shorthead);
+
+       return 0;
+}
+
+static int init_basic_state(struct replay_opts *opts, const char *head_name,
+                           struct commit *onto, const char *orig_head)
+{
+       FILE *interactive;
+
+       if (!is_directory(merge_dir()) && mkdir_in_gitdir(merge_dir()))
+               return error_errno(_("could not create temporary %s"), merge_dir());
+
+       delete_reflog("REBASE_HEAD");
+
+       interactive = fopen(path_interactive(), "w");
+       if (!interactive)
+               return error_errno(_("could not mark as interactive"));
+       fclose(interactive);
+
+       return write_basic_state(opts, head_name, onto, orig_head);
+}
+
+static void split_exec_commands(const char *cmd, struct string_list *commands)
+{
+       if (cmd && *cmd) {
+               string_list_split(commands, cmd, '\n', -1);
+
+               /* rebase.c adds a new line to cmd after every command,
+                * so here the last command is always empty */
+               string_list_remove_empty_items(commands, 0);
+       }
+}
+
+static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
+{
+       int ret;
+       const char *head_hash = NULL;
+       char *revisions = NULL, *shortrevisions = NULL;
+       struct argv_array make_script_args = ARGV_ARRAY_INIT;
+       struct todo_list todo_list = TODO_LIST_INIT;
+       struct replay_opts replay = get_replay_opts(opts);
+       struct string_list commands = STRING_LIST_INIT_DUP;
+
+       if (prepare_branch_to_be_rebased(the_repository, &replay,
+                                        opts->switch_to))
+               return -1;
+
+       if (get_revision_ranges(opts->upstream, opts->onto, &head_hash,
+                               &revisions, &shortrevisions))
+               return -1;
+
+       if (init_basic_state(&replay,
+                            opts->head_name ? opts->head_name : "detached HEAD",
+                            opts->onto, head_hash)) {
+               free(revisions);
+               free(shortrevisions);
+
+               return -1;
+       }
+
+       if (!opts->upstream && opts->squash_onto)
+               write_file(path_squash_onto(), "%s\n",
+                          oid_to_hex(opts->squash_onto));
+
+       argv_array_pushl(&make_script_args, "", revisions, NULL);
+       if (opts->restrict_revision)
+               argv_array_push(&make_script_args,
+                               oid_to_hex(&opts->restrict_revision->object.oid));
+
+       ret = sequencer_make_script(the_repository, &todo_list.buf,
+                                   make_script_args.argc, make_script_args.argv,
+                                   flags);
+
+       if (ret)
+               error(_("could not generate todo list"));
+       else {
+               discard_cache();
+               if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
+                                               &todo_list))
+                       BUG("unusable todo list");
+
+               split_exec_commands(opts->cmd, &commands);
+               ret = complete_action(the_repository, &replay, flags,
+                       shortrevisions, opts->onto_name, opts->onto, head_hash,
+                       &commands, opts->autosquash, &todo_list);
+       }
+
+       string_list_clear(&commands, 0);
+       free(revisions);
+       free(shortrevisions);
+       todo_list_release(&todo_list);
+       argv_array_clear(&make_script_args);
+
+       return ret;
+}
+
+static int run_rebase_interactive(struct rebase_options *opts,
+                                 enum action command)
+{
+       unsigned flags = 0;
+       int abbreviate_commands = 0, ret = 0;
+
+       git_config_get_bool("rebase.abbreviatecommands", &abbreviate_commands);
+
+       flags |= opts->keep_empty ? TODO_LIST_KEEP_EMPTY : 0;
+       flags |= abbreviate_commands ? TODO_LIST_ABBREVIATE_CMDS : 0;
+       flags |= opts->rebase_merges ? TODO_LIST_REBASE_MERGES : 0;
+       flags |= opts->rebase_cousins > 0 ? TODO_LIST_REBASE_COUSINS : 0;
+       flags |= command == ACTION_SHORTEN_OIDS ? TODO_LIST_SHORTEN_IDS : 0;
+
+       switch (command) {
+       case ACTION_NONE: {
+               if (!opts->onto && !opts->upstream)
+                       die(_("a base commit must be provided with --upstream or --onto"));
+
+               ret = do_interactive_rebase(opts, flags);
+               break;
+       }
+       case ACTION_SKIP: {
+               struct string_list merge_rr = STRING_LIST_INIT_DUP;
+
+               rerere_clear(the_repository, &merge_rr);
+       }
+               /* fallthrough */
+       case ACTION_CONTINUE: {
+               struct replay_opts replay_opts = get_replay_opts(opts);
+
+               ret = sequencer_continue(the_repository, &replay_opts);
+               break;
+       }
+       case ACTION_EDIT_TODO:
+               ret = edit_todo_file(flags);
+               break;
+       case ACTION_SHOW_CURRENT_PATCH: {
+               struct child_process cmd = CHILD_PROCESS_INIT;
+
+               cmd.git_cmd = 1;
+               argv_array_pushl(&cmd.args, "show", "REBASE_HEAD", "--", NULL);
+               ret = run_command(&cmd);
+
+               break;
+       }
+       case ACTION_SHORTEN_OIDS:
+       case ACTION_EXPAND_OIDS:
+               ret = transform_todo_file(flags);
+               break;
+       case ACTION_CHECK_TODO_LIST:
+               ret = check_todo_list_from_file(the_repository);
+               break;
+       case ACTION_REARRANGE_SQUASH:
+               ret = rearrange_squash_in_todo_file();
+               break;
+       case ACTION_ADD_EXEC: {
+               struct string_list commands = STRING_LIST_INIT_DUP;
+
+               split_exec_commands(opts->cmd, &commands);
+               ret = add_exec_commands(&commands);
+               string_list_clear(&commands, 0);
+               break;
+       }
+       default:
+               BUG("invalid command '%d'", command);
+       }
+
+       return ret;
+}
+
+static const char * const builtin_rebase_interactive_usage[] = {
+       N_("git rebase--interactive [<options>]"),
+       NULL
 };
 
+int cmd_rebase__interactive(int argc, const char **argv, const char *prefix)
+{
+       struct rebase_options opts = REBASE_OPTIONS_INIT;
+       struct object_id squash_onto = null_oid;
+       enum action command = ACTION_NONE;
+       struct option options[] = {
+               OPT_NEGBIT(0, "ff", &opts.flags, N_("allow fast-forward"),
+                          REBASE_FORCE),
+               OPT_BOOL(0, "keep-empty", &opts.keep_empty, N_("keep empty commits")),
+               OPT_BOOL(0, "allow-empty-message", &opts.allow_empty_message,
+                        N_("allow commits with empty messages")),
+               OPT_BOOL(0, "rebase-merges", &opts.rebase_merges, N_("rebase merge commits")),
+               OPT_BOOL(0, "rebase-cousins", &opts.rebase_cousins,
+                        N_("keep original branch points of cousins")),
+               OPT_BOOL(0, "autosquash", &opts.autosquash,
+                        N_("move commits that begin with squash!/fixup!")),
+               OPT_BOOL(0, "signoff", &opts.signoff, N_("sign commits")),
+               OPT_BIT('v', "verbose", &opts.flags,
+                       N_("display a diffstat of what changed upstream"),
+                       REBASE_NO_QUIET | REBASE_VERBOSE | REBASE_DIFFSTAT),
+               OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
+                           ACTION_CONTINUE),
+               OPT_CMDMODE(0, "skip", &command, N_("skip commit"), ACTION_SKIP),
+               OPT_CMDMODE(0, "edit-todo", &command, N_("edit the todo list"),
+                           ACTION_EDIT_TODO),
+               OPT_CMDMODE(0, "show-current-patch", &command, N_("show the current patch"),
+                           ACTION_SHOW_CURRENT_PATCH),
+               OPT_CMDMODE(0, "shorten-ids", &command,
+                       N_("shorten commit ids in the todo list"), ACTION_SHORTEN_OIDS),
+               OPT_CMDMODE(0, "expand-ids", &command,
+                       N_("expand commit ids in the todo list"), ACTION_EXPAND_OIDS),
+               OPT_CMDMODE(0, "check-todo-list", &command,
+                       N_("check the todo list"), ACTION_CHECK_TODO_LIST),
+               OPT_CMDMODE(0, "rearrange-squash", &command,
+                       N_("rearrange fixup/squash lines"), ACTION_REARRANGE_SQUASH),
+               OPT_CMDMODE(0, "add-exec-commands", &command,
+                       N_("insert exec commands in todo list"), ACTION_ADD_EXEC),
+               { OPTION_CALLBACK, 0, "onto", &opts.onto, N_("onto"), N_("onto"),
+                 PARSE_OPT_NONEG, parse_opt_commit, 0 },
+               { OPTION_CALLBACK, 0, "restrict-revision", &opts.restrict_revision,
+                 N_("restrict-revision"), N_("restrict revision"),
+                 PARSE_OPT_NONEG, parse_opt_commit, 0 },
+               { OPTION_CALLBACK, 0, "squash-onto", &squash_onto, N_("squash-onto"),
+                 N_("squash onto"), PARSE_OPT_NONEG, parse_opt_object_id, 0 },
+               { OPTION_CALLBACK, 0, "upstream", &opts.upstream, N_("upstream"),
+                 N_("the upstream commit"), PARSE_OPT_NONEG, parse_opt_commit,
+                 0 },
+               OPT_STRING(0, "head-name", &opts.head_name, N_("head-name"), N_("head name")),
+               { OPTION_STRING, 'S', "gpg-sign", &opts.gpg_sign_opt, N_("key-id"),
+                       N_("GPG-sign commits"),
+                       PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+               OPT_STRING(0, "strategy", &opts.strategy, N_("strategy"),
+                          N_("rebase strategy")),
+               OPT_STRING(0, "strategy-opts", &opts.strategy_opts, N_("strategy-opts"),
+                          N_("strategy options")),
+               OPT_STRING(0, "switch-to", &opts.switch_to, N_("switch-to"),
+                          N_("the branch or commit to checkout")),
+               OPT_STRING(0, "onto-name", &opts.onto_name, N_("onto-name"), N_("onto name")),
+               OPT_STRING(0, "cmd", &opts.cmd, N_("cmd"), N_("the command to run")),
+               OPT_RERERE_AUTOUPDATE(&opts.allow_rerere_autoupdate),
+               OPT_BOOL(0, "reschedule-failed-exec", &opts.reschedule_failed_exec,
+                        N_("automatically re-schedule any `exec` that fails")),
+               OPT_END()
+       };
+
+       opts.rebase_cousins = -1;
+
+       if (argc == 1)
+               usage_with_options(builtin_rebase_interactive_usage, options);
+
+       argc = parse_options(argc, argv, prefix, options,
+                       builtin_rebase_interactive_usage, PARSE_OPT_KEEP_ARGV0);
+
+       if (!is_null_oid(&squash_onto))
+               opts.squash_onto = &squash_onto;
+
+       if (opts.rebase_cousins >= 0 && !opts.rebase_merges)
+               warning(_("--[no-]rebase-cousins has no effect without "
+                         "--rebase-merges"));
+
+       return !!run_rebase_interactive(&opts, command);
+}
+
 static int is_interactive(struct rebase_options *opts)
 {
        return opts->type == REBASE_INTERACTIVE ||
                opts->type == REBASE_PRESERVE_MERGES;
 }
 
+static void imply_interactive(struct rebase_options *opts, const char *option)
+{
+       switch (opts->type) {
+       case REBASE_AM:
+               die(_("%s requires an interactive rebase"), option);
+               break;
+       case REBASE_INTERACTIVE:
+       case REBASE_PRESERVE_MERGES:
+               break;
+       case REBASE_MERGE:
+               /* we now implement --merge via --interactive */
+       default:
+               opts->type = REBASE_INTERACTIVE; /* implied */
+               break;
+       }
+}
+
 /* Returns the filename prefixed by the state_dir */
 static const char *state_dir_path(const char *filename, struct rebase_options *opts)
 {
@@ -113,91 +560,609 @@ static const char *state_dir_path(const char *filename, struct rebase_options *o
        return path.buf;
 }
 
-static int finish_rebase(struct rebase_options *opts)
+/* Read one file, then strip line endings */
+static int read_one(const char *path, struct strbuf *buf)
+{
+       if (strbuf_read_file(buf, path, 0) < 0)
+               return error_errno(_("could not read '%s'"), path);
+       strbuf_trim_trailing_newline(buf);
+       return 0;
+}
+
+/* Initialize the rebase options from the state directory. */
+static int read_basic_state(struct rebase_options *opts)
+{
+       struct strbuf head_name = STRBUF_INIT;
+       struct strbuf buf = STRBUF_INIT;
+       struct object_id oid;
+
+       if (read_one(state_dir_path("head-name", opts), &head_name) ||
+           read_one(state_dir_path("onto", opts), &buf))
+               return -1;
+       opts->head_name = starts_with(head_name.buf, "refs/") ?
+               xstrdup(head_name.buf) : NULL;
+       strbuf_release(&head_name);
+       if (get_oid(buf.buf, &oid))
+               return error(_("could not get 'onto': '%s'"), buf.buf);
+       opts->onto = lookup_commit_or_die(&oid, buf.buf);
+
+       /*
+        * We always write to orig-head, but interactive rebase used to write to
+        * head. Fall back to reading from head to cover for the case that the
+        * user upgraded git with an ongoing interactive rebase.
+        */
+       strbuf_reset(&buf);
+       if (file_exists(state_dir_path("orig-head", opts))) {
+               if (read_one(state_dir_path("orig-head", opts), &buf))
+                       return -1;
+       } else if (read_one(state_dir_path("head", opts), &buf))
+               return -1;
+       if (get_oid(buf.buf, &opts->orig_head))
+               return error(_("invalid orig-head: '%s'"), buf.buf);
+
+       if (file_exists(state_dir_path("quiet", opts)))
+               opts->flags &= ~REBASE_NO_QUIET;
+       else
+               opts->flags |= REBASE_NO_QUIET;
+
+       if (file_exists(state_dir_path("verbose", opts)))
+               opts->flags |= REBASE_VERBOSE;
+
+       if (file_exists(state_dir_path("signoff", opts))) {
+               opts->signoff = 1;
+               opts->flags |= REBASE_FORCE;
+       }
+
+       if (file_exists(state_dir_path("allow_rerere_autoupdate", opts))) {
+               strbuf_reset(&buf);
+               if (read_one(state_dir_path("allow_rerere_autoupdate", opts),
+                           &buf))
+                       return -1;
+               if (!strcmp(buf.buf, "--rerere-autoupdate"))
+                       opts->allow_rerere_autoupdate = RERERE_AUTOUPDATE;
+               else if (!strcmp(buf.buf, "--no-rerere-autoupdate"))
+                       opts->allow_rerere_autoupdate = RERERE_NOAUTOUPDATE;
+               else
+                       warning(_("ignoring invalid allow_rerere_autoupdate: "
+                                 "'%s'"), buf.buf);
+       }
+
+       if (file_exists(state_dir_path("gpg_sign_opt", opts))) {
+               strbuf_reset(&buf);
+               if (read_one(state_dir_path("gpg_sign_opt", opts),
+                           &buf))
+                       return -1;
+               free(opts->gpg_sign_opt);
+               opts->gpg_sign_opt = xstrdup(buf.buf);
+       }
+
+       if (file_exists(state_dir_path("strategy", opts))) {
+               strbuf_reset(&buf);
+               if (read_one(state_dir_path("strategy", opts), &buf))
+                       return -1;
+               free(opts->strategy);
+               opts->strategy = xstrdup(buf.buf);
+       }
+
+       if (file_exists(state_dir_path("strategy_opts", opts))) {
+               strbuf_reset(&buf);
+               if (read_one(state_dir_path("strategy_opts", opts), &buf))
+                       return -1;
+               free(opts->strategy_opts);
+               opts->strategy_opts = xstrdup(buf.buf);
+       }
+
+       strbuf_release(&buf);
+
+       return 0;
+}
+
+static int rebase_write_basic_state(struct rebase_options *opts)
+{
+       write_file(state_dir_path("head-name", opts), "%s",
+                  opts->head_name ? opts->head_name : "detached HEAD");
+       write_file(state_dir_path("onto", opts), "%s",
+                  opts->onto ? oid_to_hex(&opts->onto->object.oid) : "");
+       write_file(state_dir_path("orig-head", opts), "%s",
+                  oid_to_hex(&opts->orig_head));
+       write_file(state_dir_path("quiet", opts), "%s",
+                  opts->flags & REBASE_NO_QUIET ? "" : "t");
+       if (opts->flags & REBASE_VERBOSE)
+               write_file(state_dir_path("verbose", opts), "%s", "");
+       if (opts->strategy)
+               write_file(state_dir_path("strategy", opts), "%s",
+                          opts->strategy);
+       if (opts->strategy_opts)
+               write_file(state_dir_path("strategy_opts", opts), "%s",
+                          opts->strategy_opts);
+       if (opts->allow_rerere_autoupdate > 0)
+               write_file(state_dir_path("allow_rerere_autoupdate", opts),
+                          "-%s-rerere-autoupdate",
+                          opts->allow_rerere_autoupdate == RERERE_AUTOUPDATE ?
+                               "" : "-no");
+       if (opts->gpg_sign_opt)
+               write_file(state_dir_path("gpg_sign_opt", opts), "%s",
+                          opts->gpg_sign_opt);
+       if (opts->signoff)
+               write_file(state_dir_path("strategy", opts), "--signoff");
+
+       return 0;
+}
+
+static int apply_autostash(struct rebase_options *opts)
+{
+       const char *path = state_dir_path("autostash", opts);
+       struct strbuf autostash = STRBUF_INIT;
+       struct child_process stash_apply = CHILD_PROCESS_INIT;
+
+       if (!file_exists(path))
+               return 0;
+
+       if (read_one(path, &autostash))
+               return error(_("Could not read '%s'"), path);
+       /* Ensure that the hash is not mistaken for a number */
+       strbuf_addstr(&autostash, "^0");
+       argv_array_pushl(&stash_apply.args,
+                        "stash", "apply", autostash.buf, NULL);
+       stash_apply.git_cmd = 1;
+       stash_apply.no_stderr = stash_apply.no_stdout =
+               stash_apply.no_stdin = 1;
+       if (!run_command(&stash_apply))
+               printf(_("Applied autostash.\n"));
+       else {
+               struct argv_array args = ARGV_ARRAY_INIT;
+               int res = 0;
+
+               argv_array_pushl(&args,
+                                "stash", "store", "-m", "autostash", "-q",
+                                autostash.buf, NULL);
+               if (run_command_v_opt(args.argv, RUN_GIT_CMD))
+                       res = error(_("Cannot store %s"), autostash.buf);
+               argv_array_clear(&args);
+               strbuf_release(&autostash);
+               if (res)
+                       return res;
+
+               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(&autostash);
+       return 0;
+}
+
+static int finish_rebase(struct rebase_options *opts)
+{
+       struct strbuf dir = STRBUF_INIT;
+       const char *argv_gc_auto[] = { "gc", "--auto", NULL };
+       int ret = 0;
+
+       delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
+       apply_autostash(opts);
+       close_object_store(the_repository->objects);
+       /*
+        * We ignore errors in 'gc --auto', since the
+        * user should see them.
+        */
+       run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
+       if (opts->type == REBASE_INTERACTIVE) {
+               struct replay_opts replay = REPLAY_OPTS_INIT;
+
+               replay.action = REPLAY_INTERACTIVE_REBASE;
+               ret = sequencer_remove_state(&replay);
+       } else {
+               strbuf_addstr(&dir, opts->state_dir);
+               if (remove_dir_recursively(&dir, 0))
+                       ret = error(_("could not remove '%s'"),
+                                   opts->state_dir);
+               strbuf_release(&dir);
+       }
+
+       return ret;
+}
+
+static struct commit *peel_committish(const char *name)
+{
+       struct object *obj;
+       struct object_id oid;
+
+       if (get_oid(name, &oid))
+               return NULL;
+       obj = parse_object(the_repository, &oid);
+       return (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
+}
+
+static void add_var(struct strbuf *buf, const char *name, const char *value)
+{
+       if (!value)
+               strbuf_addf(buf, "unset %s; ", name);
+       else {
+               strbuf_addf(buf, "%s=", name);
+               sq_quote_buf(buf, value);
+               strbuf_addstr(buf, "; ");
+       }
+}
+
+#define GIT_REFLOG_ACTION_ENVIRONMENT "GIT_REFLOG_ACTION"
+
+#define RESET_HEAD_DETACH (1<<0)
+#define RESET_HEAD_HARD (1<<1)
+#define RESET_HEAD_RUN_POST_CHECKOUT_HOOK (1<<2)
+#define RESET_HEAD_REFS_ONLY (1<<3)
+#define RESET_ORIG_HEAD (1<<4)
+
+static int reset_head(struct object_id *oid, const char *action,
+                     const char *switch_to_branch, unsigned flags,
+                     const char *reflog_orig_head, const char *reflog_head)
+{
+       unsigned detach_head = flags & RESET_HEAD_DETACH;
+       unsigned reset_hard = flags & RESET_HEAD_HARD;
+       unsigned run_hook = flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
+       unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
+       unsigned update_orig_head = flags & RESET_ORIG_HEAD;
+       struct object_id head_oid;
+       struct tree_desc desc[2] = { { NULL }, { NULL } };
+       struct lock_file lock = LOCK_INIT;
+       struct unpack_trees_options unpack_tree_opts;
+       struct tree *tree;
+       const char *reflog_action;
+       struct strbuf msg = STRBUF_INIT;
+       size_t prefix_len;
+       struct object_id *orig = NULL, oid_orig,
+               *old_orig = NULL, oid_old_orig;
+       int ret = 0, nr = 0;
+
+       if (switch_to_branch && !starts_with(switch_to_branch, "refs/"))
+               BUG("Not a fully qualified branch: '%s'", switch_to_branch);
+
+       if (!refs_only && hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0) {
+               ret = -1;
+               goto leave_reset_head;
+       }
+
+       if ((!oid || !reset_hard) && get_oid("HEAD", &head_oid)) {
+               ret = error(_("could not determine HEAD revision"));
+               goto leave_reset_head;
+       }
+
+       if (!oid)
+               oid = &head_oid;
+
+       if (refs_only)
+               goto reset_head_refs;
+
+       memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
+       setup_unpack_trees_porcelain(&unpack_tree_opts, action);
+       unpack_tree_opts.head_idx = 1;
+       unpack_tree_opts.src_index = the_repository->index;
+       unpack_tree_opts.dst_index = the_repository->index;
+       unpack_tree_opts.fn = reset_hard ? oneway_merge : twoway_merge;
+       unpack_tree_opts.update = 1;
+       unpack_tree_opts.merge = 1;
+       if (!detach_head)
+               unpack_tree_opts.reset = 1;
+
+       if (repo_read_index_unmerged(the_repository) < 0) {
+               ret = error(_("could not read index"));
+               goto leave_reset_head;
+       }
+
+       if (!reset_hard && !fill_tree_descriptor(the_repository, &desc[nr++], &head_oid)) {
+               ret = error(_("failed to find tree of %s"),
+                           oid_to_hex(&head_oid));
+               goto leave_reset_head;
+       }
+
+       if (!fill_tree_descriptor(the_repository, &desc[nr++], oid)) {
+               ret = error(_("failed to find tree of %s"), oid_to_hex(oid));
+               goto leave_reset_head;
+       }
+
+       if (unpack_trees(nr, desc, &unpack_tree_opts)) {
+               ret = -1;
+               goto leave_reset_head;
+       }
+
+       tree = parse_tree_indirect(oid);
+       prime_cache_tree(the_repository, the_repository->index, tree);
+
+       if (write_locked_index(the_repository->index, &lock, COMMIT_LOCK) < 0) {
+               ret = error(_("could not write index"));
+               goto leave_reset_head;
+       }
+
+reset_head_refs:
+       reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
+       strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : "rebase");
+       prefix_len = msg.len;
+
+       if (update_orig_head) {
+               if (!get_oid("ORIG_HEAD", &oid_old_orig))
+                       old_orig = &oid_old_orig;
+               if (!get_oid("HEAD", &oid_orig)) {
+                       orig = &oid_orig;
+                       if (!reflog_orig_head) {
+                               strbuf_addstr(&msg, "updating ORIG_HEAD");
+                               reflog_orig_head = msg.buf;
+                       }
+                       update_ref(reflog_orig_head, "ORIG_HEAD", orig,
+                                  old_orig, 0, UPDATE_REFS_MSG_ON_ERR);
+               } else if (old_orig)
+                       delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
+       }
+
+       if (!reflog_head) {
+               strbuf_setlen(&msg, prefix_len);
+               strbuf_addstr(&msg, "updating HEAD");
+               reflog_head = msg.buf;
+       }
+       if (!switch_to_branch)
+               ret = update_ref(reflog_head, "HEAD", oid, orig,
+                                detach_head ? REF_NO_DEREF : 0,
+                                UPDATE_REFS_MSG_ON_ERR);
+       else {
+               ret = update_ref(reflog_head, switch_to_branch, oid,
+                                NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+               if (!ret)
+                       ret = create_symref("HEAD", switch_to_branch,
+                                           reflog_head);
+       }
+       if (run_hook)
+               run_hook_le(NULL, "post-checkout",
+                           oid_to_hex(orig ? orig : &null_oid),
+                           oid_to_hex(oid), "1", NULL);
+
+leave_reset_head:
+       strbuf_release(&msg);
+       rollback_lock_file(&lock);
+       while (nr)
+               free((void *)desc[--nr].buffer);
+       return ret;
+}
+
+static int move_to_original_branch(struct rebase_options *opts)
 {
-       struct strbuf dir = STRBUF_INIT;
-       const char *argv_gc_auto[] = { "gc", "--auto", NULL };
+       struct strbuf orig_head_reflog = STRBUF_INIT, head_reflog = STRBUF_INIT;
+       int ret;
 
-       delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
-       apply_autostash();
-       close_all_packs(the_repository->objects);
-       /*
-        * We ignore errors in 'gc --auto', since the
-        * user should see them.
-        */
-       run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
-       strbuf_addstr(&dir, opts->state_dir);
-       remove_dir_recursively(&dir, 0);
-       strbuf_release(&dir);
+       if (!opts->head_name)
+               return 0; /* nothing to move back to */
 
-       return 0;
-}
+       if (!opts->onto)
+               BUG("move_to_original_branch without onto");
 
-static struct commit *peel_committish(const char *name)
-{
-       struct object *obj;
-       struct object_id oid;
+       strbuf_addf(&orig_head_reflog, "rebase finished: %s onto %s",
+                   opts->head_name, oid_to_hex(&opts->onto->object.oid));
+       strbuf_addf(&head_reflog, "rebase finished: returning to %s",
+                   opts->head_name);
+       ret = reset_head(NULL, "", opts->head_name, RESET_HEAD_REFS_ONLY,
+                        orig_head_reflog.buf, head_reflog.buf);
 
-       if (get_oid(name, &oid))
-               return NULL;
-       obj = parse_object(the_repository, &oid);
-       return (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
+       strbuf_release(&orig_head_reflog);
+       strbuf_release(&head_reflog);
+       return ret;
 }
 
-static void add_var(struct strbuf *buf, const char *name, const char *value)
+static const char *resolvemsg =
+N_("Resolve all conflicts manually, mark them as resolved with\n"
+"\"git add/rm <conflicted_files>\", then run \"git rebase --continue\".\n"
+"You can instead skip this commit: run \"git rebase --skip\".\n"
+"To abort and get back to the state before \"git rebase\", run "
+"\"git rebase --abort\".");
+
+static int run_am(struct rebase_options *opts)
 {
-       if (!value)
-               strbuf_addf(buf, "unset %s; ", name);
-       else {
-               strbuf_addf(buf, "%s=", name);
-               sq_quote_buf(buf, value);
-               strbuf_addstr(buf, "; ");
+       struct child_process am = CHILD_PROCESS_INIT;
+       struct child_process format_patch = CHILD_PROCESS_INIT;
+       struct strbuf revisions = STRBUF_INIT;
+       int status;
+       char *rebased_patches;
+
+       am.git_cmd = 1;
+       argv_array_push(&am.args, "am");
+
+       if (opts->action && !strcmp("continue", opts->action)) {
+               argv_array_push(&am.args, "--resolved");
+               argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
+               if (opts->gpg_sign_opt)
+                       argv_array_push(&am.args, opts->gpg_sign_opt);
+               status = run_command(&am);
+               if (status)
+                       return status;
+
+               return move_to_original_branch(opts);
+       }
+       if (opts->action && !strcmp("skip", opts->action)) {
+               argv_array_push(&am.args, "--skip");
+               argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
+               status = run_command(&am);
+               if (status)
+                       return status;
+
+               return move_to_original_branch(opts);
+       }
+       if (opts->action && !strcmp("show-current-patch", opts->action)) {
+               argv_array_push(&am.args, "--show-current-patch");
+               return run_command(&am);
+       }
+
+       strbuf_addf(&revisions, "%s...%s",
+                   oid_to_hex(opts->root ?
+                              /* this is now equivalent to !opts->upstream */
+                              &opts->onto->object.oid :
+                              &opts->upstream->object.oid),
+                   oid_to_hex(&opts->orig_head));
+
+       rebased_patches = xstrdup(git_path("rebased-patches"));
+       format_patch.out = open(rebased_patches,
+                               O_WRONLY | O_CREAT | O_TRUNC, 0666);
+       if (format_patch.out < 0) {
+               status = error_errno(_("could not open '%s' for writing"),
+                                    rebased_patches);
+               free(rebased_patches);
+               argv_array_clear(&am.args);
+               return status;
        }
+
+       format_patch.git_cmd = 1;
+       argv_array_pushl(&format_patch.args, "format-patch", "-k", "--stdout",
+                        "--full-index", "--cherry-pick", "--right-only",
+                        "--src-prefix=a/", "--dst-prefix=b/", "--no-renames",
+                        "--no-cover-letter", "--pretty=mboxrd", "--topo-order", NULL);
+       if (opts->git_format_patch_opt.len)
+               argv_array_split(&format_patch.args,
+                                opts->git_format_patch_opt.buf);
+       argv_array_push(&format_patch.args, revisions.buf);
+       if (opts->restrict_revision)
+               argv_array_pushf(&format_patch.args, "^%s",
+                                oid_to_hex(&opts->restrict_revision->object.oid));
+
+       status = run_command(&format_patch);
+       if (status) {
+               unlink(rebased_patches);
+               free(rebased_patches);
+               argv_array_clear(&am.args);
+
+               reset_head(&opts->orig_head, "checkout", opts->head_name, 0,
+                          "HEAD", NULL);
+               error(_("\ngit encountered an error while preparing the "
+                       "patches to replay\n"
+                       "these revisions:\n"
+                       "\n    %s\n\n"
+                       "As a result, git cannot rebase them."),
+                     opts->revisions);
+
+               strbuf_release(&revisions);
+               return status;
+       }
+       strbuf_release(&revisions);
+
+       am.in = open(rebased_patches, O_RDONLY);
+       if (am.in < 0) {
+               status = error_errno(_("could not open '%s' for reading"),
+                                    rebased_patches);
+               free(rebased_patches);
+               argv_array_clear(&am.args);
+               return status;
+       }
+
+       argv_array_pushv(&am.args, opts->git_am_opts.argv);
+       argv_array_push(&am.args, "--rebasing");
+       argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
+       argv_array_push(&am.args, "--patch-format=mboxrd");
+       if (opts->allow_rerere_autoupdate == RERERE_AUTOUPDATE)
+               argv_array_push(&am.args, "--rerere-autoupdate");
+       else if (opts->allow_rerere_autoupdate == RERERE_NOAUTOUPDATE)
+               argv_array_push(&am.args, "--no-rerere-autoupdate");
+       if (opts->gpg_sign_opt)
+               argv_array_push(&am.args, opts->gpg_sign_opt);
+       status = run_command(&am);
+       unlink(rebased_patches);
+       free(rebased_patches);
+
+       if (!status) {
+               return move_to_original_branch(opts);
+       }
+
+       if (is_directory(opts->state_dir))
+               rebase_write_basic_state(opts);
+
+       return status;
 }
 
-static int run_specific_rebase(struct rebase_options *opts)
+static int run_specific_rebase(struct rebase_options *opts, enum action action)
 {
        const char *argv[] = { NULL, NULL };
-       struct strbuf script_snippet = STRBUF_INIT;
+       struct strbuf script_snippet = STRBUF_INIT, buf = STRBUF_INIT;
        int status;
        const char *backend, *backend_func;
 
+       if (opts->type == REBASE_INTERACTIVE) {
+               /* Run builtin interactive rebase */
+               setenv("GIT_CHERRY_PICK_HELP", resolvemsg, 1);
+               if (!(opts->flags & REBASE_INTERACTIVE_EXPLICIT)) {
+                       setenv("GIT_SEQUENCE_EDITOR", ":", 1);
+                       opts->autosquash = 0;
+               }
+               if (opts->gpg_sign_opt) {
+                       /* remove the leading "-S" */
+                       char *tmp = xstrdup(opts->gpg_sign_opt + 2);
+                       free(opts->gpg_sign_opt);
+                       opts->gpg_sign_opt = tmp;
+               }
+
+               status = run_rebase_interactive(opts, action);
+               goto finished_rebase;
+       }
+
+       if (opts->type == REBASE_AM) {
+               status = run_am(opts);
+               goto finished_rebase;
+       }
+
        add_var(&script_snippet, "GIT_DIR", absolute_path(get_git_dir()));
        add_var(&script_snippet, "state_dir", opts->state_dir);
 
        add_var(&script_snippet, "upstream_name", opts->upstream_name);
-       add_var(&script_snippet, "upstream",
-                                oid_to_hex(&opts->upstream->object.oid));
-       add_var(&script_snippet, "head_name", opts->head_name);
+       add_var(&script_snippet, "upstream", opts->upstream ?
+               oid_to_hex(&opts->upstream->object.oid) : NULL);
+       add_var(&script_snippet, "head_name",
+               opts->head_name ? opts->head_name : "detached HEAD");
        add_var(&script_snippet, "orig_head", oid_to_hex(&opts->orig_head));
-       add_var(&script_snippet, "onto", oid_to_hex(&opts->onto->object.oid));
+       add_var(&script_snippet, "onto", opts->onto ?
+               oid_to_hex(&opts->onto->object.oid) : NULL);
        add_var(&script_snippet, "onto_name", opts->onto_name);
        add_var(&script_snippet, "revisions", opts->revisions);
        add_var(&script_snippet, "restrict_revision", opts->restrict_revision ?
                oid_to_hex(&opts->restrict_revision->object.oid) : NULL);
        add_var(&script_snippet, "GIT_QUIET",
                opts->flags & REBASE_NO_QUIET ? "" : "t");
-       add_var(&script_snippet, "git_am_opt", opts->git_am_opt.buf);
+       sq_quote_argv_pretty(&buf, opts->git_am_opts.argv);
+       add_var(&script_snippet, "git_am_opt", buf.buf);
+       strbuf_release(&buf);
        add_var(&script_snippet, "verbose",
                opts->flags & REBASE_VERBOSE ? "t" : "");
        add_var(&script_snippet, "diffstat",
                opts->flags & REBASE_DIFFSTAT ? "t" : "");
        add_var(&script_snippet, "force_rebase",
                opts->flags & REBASE_FORCE ? "t" : "");
+       if (opts->switch_to)
+               add_var(&script_snippet, "switch_to", opts->switch_to);
+       add_var(&script_snippet, "action", opts->action ? opts->action : "");
+       add_var(&script_snippet, "signoff", opts->signoff ? "--signoff" : "");
+       add_var(&script_snippet, "allow_rerere_autoupdate",
+               opts->allow_rerere_autoupdate ?
+                       opts->allow_rerere_autoupdate == RERERE_AUTOUPDATE ?
+                       "--rerere-autoupdate" : "--no-rerere-autoupdate" : "");
+       add_var(&script_snippet, "keep_empty", opts->keep_empty ? "yes" : "");
+       add_var(&script_snippet, "autosquash", opts->autosquash ? "t" : "");
+       add_var(&script_snippet, "gpg_sign_opt", opts->gpg_sign_opt);
+       add_var(&script_snippet, "cmd", opts->cmd);
+       add_var(&script_snippet, "allow_empty_message",
+               opts->allow_empty_message ?  "--allow-empty-message" : "");
+       add_var(&script_snippet, "rebase_merges",
+               opts->rebase_merges ? "t" : "");
+       add_var(&script_snippet, "rebase_cousins",
+               opts->rebase_cousins ? "t" : "");
+       add_var(&script_snippet, "strategy", opts->strategy);
+       add_var(&script_snippet, "strategy_opts", opts->strategy_opts);
+       add_var(&script_snippet, "rebase_root", opts->root ? "t" : "");
+       add_var(&script_snippet, "squash_onto",
+               opts->squash_onto ? oid_to_hex(opts->squash_onto) : "");
+       add_var(&script_snippet, "git_format_patch_opt",
+               opts->git_format_patch_opt.buf);
+
+       if (is_interactive(opts) &&
+           !(opts->flags & REBASE_INTERACTIVE_EXPLICIT)) {
+               strbuf_addstr(&script_snippet,
+                             "GIT_SEQUENCE_EDITOR=:; export GIT_SEQUENCE_EDITOR; ");
+               opts->autosquash = 0;
+       }
 
        switch (opts->type) {
-       case REBASE_AM:
-               backend = "git-rebase--am";
-               backend_func = "git_rebase__am";
-               break;
-       case REBASE_INTERACTIVE:
-               backend = "git-rebase--interactive";
-               backend_func = "git_rebase__interactive";
-               break;
-       case REBASE_MERGE:
-               backend = "git-rebase--merge";
-               backend_func = "git_rebase__merge";
-               break;
        case REBASE_PRESERVE_MERGES:
                backend = "git-rebase--preserve-merges";
                backend_func = "git_rebase__preserve_merges";
@@ -208,20 +1173,22 @@ static int run_specific_rebase(struct rebase_options *opts)
        }
 
        strbuf_addf(&script_snippet,
-                   ". git-sh-setup && . git-rebase--common &&"
-                   " . %s && %s", backend, backend_func);
+                   ". git-sh-setup && . %s && %s", backend, backend_func);
        argv[0] = script_snippet.buf;
 
        status = run_command_v_opt(argv, RUN_USING_SHELL);
+finished_rebase:
        if (opts->dont_finish_rebase)
                ; /* do nothing */
+       else if (opts->type == REBASE_INTERACTIVE)
+               ; /* interactive rebase cleans up after itself */
        else if (status == 0) {
                if (!file_exists(state_dir_path("stopped-sha", opts)))
                        finish_rebase(opts);
        } else if (status == 2) {
                struct strbuf dir = STRBUF_INIT;
 
-               apply_autostash();
+               apply_autostash(opts);
                strbuf_addstr(&dir, opts->state_dir);
                remove_dir_recursively(&dir, 0);
                strbuf_release(&dir);
@@ -233,111 +1200,42 @@ static int run_specific_rebase(struct rebase_options *opts)
        return status ? -1 : 0;
 }
 
-#define GIT_REFLOG_ACTION_ENVIRONMENT "GIT_REFLOG_ACTION"
-
-static int reset_head(struct object_id *oid, const char *action,
-                     const char *switch_to_branch, int detach_head)
+static int rebase_config(const char *var, const char *value, void *data)
 {
-       struct object_id head_oid;
-       struct tree_desc desc;
-       struct lock_file lock = LOCK_INIT;
-       struct unpack_trees_options unpack_tree_opts;
-       struct tree *tree;
-       const char *reflog_action;
-       struct strbuf msg = STRBUF_INIT;
-       size_t prefix_len;
-       struct object_id *orig = NULL, oid_orig,
-               *old_orig = NULL, oid_old_orig;
-       int ret = 0;
-
-       if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
-               return -1;
+       struct rebase_options *opts = data;
 
-       if (!oid) {
-               if (get_oid("HEAD", &head_oid)) {
-                       rollback_lock_file(&lock);
-                       return error(_("could not determine HEAD revision"));
-               }
-               oid = &head_oid;
+       if (!strcmp(var, "rebase.stat")) {
+               if (git_config_bool(var, value))
+                       opts->flags |= REBASE_DIFFSTAT;
+               else
+                       opts->flags &= ~REBASE_DIFFSTAT;
+               return 0;
        }
 
-       memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
-       setup_unpack_trees_porcelain(&unpack_tree_opts, action);
-       unpack_tree_opts.head_idx = 1;
-       unpack_tree_opts.src_index = the_repository->index;
-       unpack_tree_opts.dst_index = the_repository->index;
-       unpack_tree_opts.fn = oneway_merge;
-       unpack_tree_opts.update = 1;
-       unpack_tree_opts.merge = 1;
-       if (!detach_head)
-               unpack_tree_opts.reset = 1;
-
-       if (read_index_unmerged(the_repository->index) < 0) {
-               rollback_lock_file(&lock);
-               return error(_("could not read index"));
+       if (!strcmp(var, "rebase.autosquash")) {
+               opts->autosquash = git_config_bool(var, value);
+               return 0;
        }
 
-       if (!fill_tree_descriptor(&desc, oid)) {
-               error(_("failed to find tree of %s"), oid_to_hex(oid));
-               rollback_lock_file(&lock);
-               free((void *)desc.buffer);
-               return -1;
+       if (!strcmp(var, "commit.gpgsign")) {
+               free(opts->gpg_sign_opt);
+               opts->gpg_sign_opt = git_config_bool(var, value) ?
+                       xstrdup("-S") : NULL;
+               return 0;
        }
 
-       if (unpack_trees(1, &desc, &unpack_tree_opts)) {
-               rollback_lock_file(&lock);
-               free((void *)desc.buffer);
-               return -1;
+       if (!strcmp(var, "rebase.autostash")) {
+               opts->autostash = git_config_bool(var, value);
+               return 0;
        }
 
-       tree = parse_tree_indirect(oid);
-       prime_cache_tree(the_repository->index, tree);
-
-       if (write_locked_index(the_repository->index, &lock, COMMIT_LOCK) < 0)
-               ret = error(_("could not write index"));
-       free((void *)desc.buffer);
-
-       if (ret)
-               return ret;
-
-       reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
-       strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : "rebase");
-       prefix_len = msg.len;
-
-       if (!get_oid("ORIG_HEAD", &oid_old_orig))
-               old_orig = &oid_old_orig;
-       if (!get_oid("HEAD", &oid_orig)) {
-               orig = &oid_orig;
-               strbuf_addstr(&msg, "updating ORIG_HEAD");
-               update_ref(msg.buf, "ORIG_HEAD", orig, old_orig, 0,
-                          UPDATE_REFS_MSG_ON_ERR);
-       } else if (old_orig)
-               delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
-       strbuf_setlen(&msg, prefix_len);
-       strbuf_addstr(&msg, "updating HEAD");
-       if (!switch_to_branch)
-               ret = update_ref(msg.buf, "HEAD", oid, orig, REF_NO_DEREF,
-                                UPDATE_REFS_MSG_ON_ERR);
-       else {
-               ret = create_symref("HEAD", switch_to_branch, msg.buf);
-               if (!ret)
-                       ret = update_ref(msg.buf, "HEAD", oid, NULL, 0,
-                                        UPDATE_REFS_MSG_ON_ERR);
+       if (!strcmp(var, "rebase.reschedulefailedexec")) {
+               opts->reschedule_failed_exec = git_config_bool(var, value);
+               return 0;
        }
 
-       strbuf_release(&msg);
-       return ret;
-}
-
-static int rebase_config(const char *var, const char *value, void *data)
-{
-       struct rebase_options *opts = data;
-
-       if (!strcmp(var, "rebase.stat")) {
-               if (git_config_bool(var, value))
-                       opts->flags |= REBASE_DIFFSTAT;
-               else
-                       opts->flags &= !REBASE_DIFFSTAT;
+       if (!strcmp(var, "rebase.usebuiltin")) {
+               opts->use_legacy_rebase = !git_config_bool(var, value);
                return 0;
        }
 
@@ -375,7 +1273,7 @@ static int can_fast_forward(struct commit *onto, struct object_id *head_oid,
        merge_bases = get_merge_bases(onto, head);
        if (merge_bases && !merge_bases->next) {
                oidcpy(merge_base, &merge_bases->item->object.oid);
-               res = !oidcmp(merge_base, &onto->object.oid);
+               res = oideq(merge_base, &onto->object.oid);
        } else {
                oidcpy(merge_base, &null_oid);
                res = 0;
@@ -384,19 +1282,114 @@ static int can_fast_forward(struct commit *onto, struct object_id *head_oid,
        return res && is_linear_history(onto, head);
 }
 
+/* -i followed by -m is still -i */
+static int parse_opt_merge(const struct option *opt, const char *arg, int unset)
+{
+       struct rebase_options *opts = opt->value;
+
+       BUG_ON_OPT_NEG(unset);
+       BUG_ON_OPT_ARG(arg);
+
+       if (!is_interactive(opts))
+               opts->type = REBASE_MERGE;
+
+       return 0;
+}
+
+/* -i followed by -p is still explicitly interactive, but -p alone is not */
+static int parse_opt_interactive(const struct option *opt, const char *arg,
+                                int unset)
+{
+       struct rebase_options *opts = opt->value;
+
+       BUG_ON_OPT_NEG(unset);
+       BUG_ON_OPT_ARG(arg);
+
+       opts->type = REBASE_INTERACTIVE;
+       opts->flags |= REBASE_INTERACTIVE_EXPLICIT;
+
+       return 0;
+}
+
+static void NORETURN error_on_missing_default_upstream(void)
+{
+       struct branch *current_branch = branch_get(NULL);
+
+       printf(_("%s\n"
+                "Please specify which branch you want to rebase against.\n"
+                "See git-rebase(1) for details.\n"
+                "\n"
+                "    git rebase '<branch>'\n"
+                "\n"),
+               current_branch ? _("There is no tracking information for "
+                       "the current branch.") :
+                       _("You are not currently on a branch."));
+
+       if (current_branch) {
+               const char *remote = current_branch->remote_name;
+
+               if (!remote)
+                       remote = _("<remote>");
+
+               printf(_("If you wish to set tracking information for this "
+                        "branch you can do so with:\n"
+                        "\n"
+                        "    git branch --set-upstream-to=%s/<branch> %s\n"
+                        "\n"),
+                      remote, current_branch->name);
+       }
+       exit(1);
+}
+
+static void set_reflog_action(struct rebase_options *options)
+{
+       const char *env;
+       struct strbuf buf = STRBUF_INIT;
+
+       if (!is_interactive(options))
+               return;
+
+       env = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
+       if (env && strcmp("rebase", env))
+               return; /* only override it if it is "rebase" */
+
+       strbuf_addf(&buf, "rebase -i (%s)", options->action);
+       setenv(GIT_REFLOG_ACTION_ENVIRONMENT, buf.buf, 1);
+       strbuf_release(&buf);
+}
+
+static int check_exec_cmd(const char *cmd)
+{
+       if (strchr(cmd, '\n'))
+               return error(_("exec commands cannot contain newlines"));
+
+       /* Does the command consist purely of whitespace? */
+       if (!cmd[strspn(cmd, " \t\r\f\v")])
+               return error(_("empty exec command"));
+
+       return 0;
+}
+
+
 int cmd_rebase(int argc, const char **argv, const char *prefix)
 {
-       struct rebase_options options = {
-               .type = REBASE_UNSPECIFIED,
-               .flags = REBASE_NO_QUIET,
-               .git_am_opt = STRBUF_INIT,
-       };
+       struct rebase_options options = REBASE_OPTIONS_INIT;
        const char *branch_name;
-       int ret, flags;
+       int ret, flags, total_argc, in_progress = 0;
        int ok_to_skip_pre_rebase = 0;
        struct strbuf msg = STRBUF_INIT;
        struct strbuf revisions = STRBUF_INIT;
+       struct strbuf buf = STRBUF_INIT;
        struct object_id merge_base;
+       enum action action = ACTION_NONE;
+       const char *gpg_sign = NULL;
+       struct string_list exec = STRING_LIST_INIT_NODUP;
+       const char *rebase_merges = NULL;
+       int fork_point = -1;
+       struct string_list strategy_options = STRING_LIST_INIT_NODUP;
+       struct object_id squash_onto;
+       char *squash_onto_name = NULL;
+       int reschedule_failed_exec = -1;
        struct option builtin_rebase_options[] = {
                OPT_STRING(0, "onto", &options.onto_name,
                           N_("revision"),
@@ -412,51 +1405,377 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                {OPTION_NEGBIT, 'n', "no-stat", &options.flags, NULL,
                        N_("do not show diffstat of what changed upstream"),
                        PARSE_OPT_NOARG, NULL, REBASE_DIFFSTAT },
+               OPT_BOOL(0, "signoff", &options.signoff,
+                        N_("add a Signed-off-by: line to each commit")),
+               OPT_PASSTHRU_ARGV(0, "ignore-whitespace", &options.git_am_opts,
+                                 NULL, N_("passed to 'git am'"),
+                                 PARSE_OPT_NOARG),
+               OPT_PASSTHRU_ARGV(0, "committer-date-is-author-date",
+                                 &options.git_am_opts, NULL,
+                                 N_("passed to 'git am'"), PARSE_OPT_NOARG),
+               OPT_PASSTHRU_ARGV(0, "ignore-date", &options.git_am_opts, NULL,
+                                 N_("passed to 'git am'"), PARSE_OPT_NOARG),
+               OPT_PASSTHRU_ARGV('C', NULL, &options.git_am_opts, N_("n"),
+                                 N_("passed to 'git apply'"), 0),
+               OPT_PASSTHRU_ARGV(0, "whitespace", &options.git_am_opts,
+                                 N_("action"), N_("passed to 'git apply'"), 0),
                OPT_BIT('f', "force-rebase", &options.flags,
                        N_("cherry-pick all commits, even if unchanged"),
                        REBASE_FORCE),
                OPT_BIT(0, "no-ff", &options.flags,
                        N_("cherry-pick all commits, even if unchanged"),
                        REBASE_FORCE),
+               OPT_CMDMODE(0, "continue", &action, N_("continue"),
+                           ACTION_CONTINUE),
+               OPT_CMDMODE(0, "skip", &action,
+                           N_("skip current patch and continue"), ACTION_SKIP),
+               OPT_CMDMODE(0, "abort", &action,
+                           N_("abort and check out the original branch"),
+                           ACTION_ABORT),
+               OPT_CMDMODE(0, "quit", &action,
+                           N_("abort but keep HEAD where it is"), ACTION_QUIT),
+               OPT_CMDMODE(0, "edit-todo", &action, N_("edit the todo list "
+                           "during an interactive rebase"), ACTION_EDIT_TODO),
+               OPT_CMDMODE(0, "show-current-patch", &action,
+                           N_("show the patch file being applied or merged"),
+                           ACTION_SHOW_CURRENT_PATCH),
+               { OPTION_CALLBACK, 'm', "merge", &options, NULL,
+                       N_("use merging strategies to rebase"),
+                       PARSE_OPT_NOARG | PARSE_OPT_NONEG,
+                       parse_opt_merge },
+               { OPTION_CALLBACK, 'i', "interactive", &options, NULL,
+                       N_("let the user edit the list of commits to rebase"),
+                       PARSE_OPT_NOARG | PARSE_OPT_NONEG,
+                       parse_opt_interactive },
+               OPT_SET_INT('p', "preserve-merges", &options.type,
+                           N_("(DEPRECATED) try to recreate merges instead of "
+                              "ignoring them"), REBASE_PRESERVE_MERGES),
+               OPT_RERERE_AUTOUPDATE(&options.allow_rerere_autoupdate),
+               OPT_BOOL('k', "keep-empty", &options.keep_empty,
+                        N_("preserve empty commits during rebase")),
+               OPT_BOOL(0, "autosquash", &options.autosquash,
+                        N_("move commits that begin with "
+                           "squash!/fixup! under -i")),
+               { OPTION_STRING, 'S', "gpg-sign", &gpg_sign, N_("key-id"),
+                       N_("GPG-sign commits"),
+                       PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+               OPT_BOOL(0, "autostash", &options.autostash,
+                        N_("automatically stash/stash pop before and after")),
+               OPT_STRING_LIST('x', "exec", &exec, N_("exec"),
+                               N_("add exec lines after each commit of the "
+                                  "editable list")),
+               OPT_BOOL(0, "allow-empty-message",
+                        &options.allow_empty_message,
+                        N_("allow rebasing commits with empty messages")),
+               {OPTION_STRING, 'r', "rebase-merges", &rebase_merges,
+                       N_("mode"),
+                       N_("try to rebase merges instead of skipping them"),
+                       PARSE_OPT_OPTARG, NULL, (intptr_t)""},
+               OPT_BOOL(0, "fork-point", &fork_point,
+                        N_("use 'merge-base --fork-point' to refine upstream")),
+               OPT_STRING('s', "strategy", &options.strategy,
+                          N_("strategy"), N_("use the given merge strategy")),
+               OPT_STRING_LIST('X', "strategy-option", &strategy_options,
+                               N_("option"),
+                               N_("pass the argument through to the merge "
+                                  "strategy")),
+               OPT_BOOL(0, "root", &options.root,
+                        N_("rebase all reachable commits up to the root(s)")),
+               OPT_BOOL(0, "reschedule-failed-exec",
+                        &reschedule_failed_exec,
+                        N_("automatically re-schedule any `exec` that fails")),
                OPT_END(),
        };
-
-       /*
-        * NEEDSWORK: Once the builtin rebase has been tested enough
-        * and git-legacy-rebase.sh is retired to contrib/, this preamble
-        * can be removed.
-        */
-
-       if (!use_builtin_rebase()) {
-               const char *path = mkpath("%s/git-legacy-rebase",
-                                         git_exec_path());
-
-               if (sane_execvp(path, (char **)argv) < 0)
-                       die_errno(_("could not exec %s"), path);
-               else
-                       BUG("sane_execvp() returned???");
-       }
+       int i;
 
        if (argc == 2 && !strcmp(argv[1], "-h"))
                usage_with_options(builtin_rebase_usage,
                                   builtin_rebase_options);
 
-       prefix = setup_git_directory();
-       trace_repo_setup(prefix);
-       setup_work_tree();
-
+       options.allow_empty_message = 1;
        git_config(rebase_config, &options);
 
+       if (options.use_legacy_rebase ||
+           !git_env_bool("GIT_TEST_REBASE_USE_BUILTIN", -1))
+               warning(_("the rebase.useBuiltin support has been removed!\n"
+                         "See its entry in 'git help config' for details."));
+
+       strbuf_reset(&buf);
+       strbuf_addf(&buf, "%s/applying", apply_dir());
+       if(file_exists(buf.buf))
+               die(_("It looks like 'git am' is in progress. Cannot rebase."));
+
+       if (is_directory(apply_dir())) {
+               options.type = REBASE_AM;
+               options.state_dir = apply_dir();
+       } else if (is_directory(merge_dir())) {
+               strbuf_reset(&buf);
+               strbuf_addf(&buf, "%s/rewritten", merge_dir());
+               if (is_directory(buf.buf)) {
+                       options.type = REBASE_PRESERVE_MERGES;
+                       options.flags |= REBASE_INTERACTIVE_EXPLICIT;
+               } else {
+                       strbuf_reset(&buf);
+                       strbuf_addf(&buf, "%s/interactive", merge_dir());
+                       if(file_exists(buf.buf)) {
+                               options.type = REBASE_INTERACTIVE;
+                               options.flags |= REBASE_INTERACTIVE_EXPLICIT;
+                       } else
+                               options.type = REBASE_MERGE;
+               }
+               options.state_dir = merge_dir();
+       }
+
+       if (options.type != REBASE_UNSPECIFIED)
+               in_progress = 1;
+
+       total_argc = argc;
        argc = parse_options(argc, argv, prefix,
                             builtin_rebase_options,
                             builtin_rebase_usage, 0);
 
+       if (action != ACTION_NONE && total_argc != 2) {
+               usage_with_options(builtin_rebase_usage,
+                                  builtin_rebase_options);
+       }
+
        if (argc > 2)
                usage_with_options(builtin_rebase_usage,
                                   builtin_rebase_options);
 
+       if (options.type == REBASE_PRESERVE_MERGES)
+               warning(_("git rebase --preserve-merges is deprecated. "
+                         "Use --rebase-merges instead."));
+
+       if (action != ACTION_NONE && !in_progress)
+               die(_("No rebase in progress?"));
+       setenv(GIT_REFLOG_ACTION_ENVIRONMENT, "rebase", 0);
+
+       if (action == ACTION_EDIT_TODO && !is_interactive(&options))
+               die(_("The --edit-todo action can only be used during "
+                     "interactive rebase."));
+
+       if (trace2_is_enabled()) {
+               if (is_interactive(&options))
+                       trace2_cmd_mode("interactive");
+               else if (exec.nr)
+                       trace2_cmd_mode("interactive-exec");
+               else
+                       trace2_cmd_mode(action_names[action]);
+       }
+
+       switch (action) {
+       case ACTION_CONTINUE: {
+               struct object_id head;
+               struct lock_file lock_file = LOCK_INIT;
+               int fd;
+
+               options.action = "continue";
+               set_reflog_action(&options);
+
+               /* Sanity check */
+               if (get_oid("HEAD", &head))
+                       die(_("Cannot read HEAD"));
+
+               fd = hold_locked_index(&lock_file, 0);
+               if (repo_read_index(the_repository) < 0)
+                       die(_("could not read index"));
+               refresh_index(the_repository->index, REFRESH_QUIET, NULL, NULL,
+                             NULL);
+               if (0 <= fd)
+                       repo_update_index_if_able(the_repository, &lock_file);
+               rollback_lock_file(&lock_file);
+
+               if (has_unstaged_changes(the_repository, 1)) {
+                       puts(_("You must edit all merge conflicts and then\n"
+                              "mark them as resolved using git add"));
+                       exit(1);
+               }
+               if (read_basic_state(&options))
+                       exit(1);
+               goto run_rebase;
+       }
+       case ACTION_SKIP: {
+               struct string_list merge_rr = STRING_LIST_INIT_DUP;
+
+               options.action = "skip";
+               set_reflog_action(&options);
+
+               rerere_clear(the_repository, &merge_rr);
+               string_list_clear(&merge_rr, 1);
+
+               if (reset_head(NULL, "reset", NULL, RESET_HEAD_HARD,
+                              NULL, NULL) < 0)
+                       die(_("could not discard worktree changes"));
+               remove_branch_state(the_repository, 0);
+               if (read_basic_state(&options))
+                       exit(1);
+               goto run_rebase;
+       }
+       case ACTION_ABORT: {
+               struct string_list merge_rr = STRING_LIST_INIT_DUP;
+               options.action = "abort";
+               set_reflog_action(&options);
+
+               rerere_clear(the_repository, &merge_rr);
+               string_list_clear(&merge_rr, 1);
+
+               if (read_basic_state(&options))
+                       exit(1);
+               if (reset_head(&options.orig_head, "reset",
+                              options.head_name, RESET_HEAD_HARD,
+                              NULL, NULL) < 0)
+                       die(_("could not move back to %s"),
+                           oid_to_hex(&options.orig_head));
+               remove_branch_state(the_repository, 0);
+               ret = !!finish_rebase(&options);
+               goto cleanup;
+       }
+       case ACTION_QUIT: {
+               if (options.type == REBASE_INTERACTIVE) {
+                       struct replay_opts replay = REPLAY_OPTS_INIT;
+
+                       replay.action = REPLAY_INTERACTIVE_REBASE;
+                       ret = !!sequencer_remove_state(&replay);
+               } else {
+                       strbuf_reset(&buf);
+                       strbuf_addstr(&buf, options.state_dir);
+                       ret = !!remove_dir_recursively(&buf, 0);
+                       if (ret)
+                               error(_("could not remove '%s'"),
+                                      options.state_dir);
+               }
+               goto cleanup;
+       }
+       case ACTION_EDIT_TODO:
+               options.action = "edit-todo";
+               options.dont_finish_rebase = 1;
+               goto run_rebase;
+       case ACTION_SHOW_CURRENT_PATCH:
+               options.action = "show-current-patch";
+               options.dont_finish_rebase = 1;
+               goto run_rebase;
+       case ACTION_NONE:
+               break;
+       default:
+               BUG("action: %d", action);
+       }
+
+       /* Make sure no rebase is in progress */
+       if (in_progress) {
+               const char *last_slash = strrchr(options.state_dir, '/');
+               const char *state_dir_base =
+                       last_slash ? last_slash + 1 : options.state_dir;
+               const char *cmd_live_rebase =
+                       "git rebase (--continue | --abort | --skip)";
+               strbuf_reset(&buf);
+               strbuf_addf(&buf, "rm -fr \"%s\"", options.state_dir);
+               die(_("It seems that there is already a %s directory, and\n"
+                     "I wonder if you are in the middle of another rebase.  "
+                     "If that is the\n"
+                     "case, please try\n\t%s\n"
+                     "If that is not the case, please\n\t%s\n"
+                     "and run me again.  I am stopping in case you still "
+                     "have something\n"
+                     "valuable there.\n"),
+                   state_dir_base, cmd_live_rebase, buf.buf);
+       }
+
+       for (i = 0; i < options.git_am_opts.argc; i++) {
+               const char *option = options.git_am_opts.argv[i], *p;
+               if (!strcmp(option, "--committer-date-is-author-date") ||
+                   !strcmp(option, "--ignore-date") ||
+                   !strcmp(option, "--whitespace=fix") ||
+                   !strcmp(option, "--whitespace=strip"))
+                       options.flags |= REBASE_FORCE;
+               else if (skip_prefix(option, "-C", &p)) {
+                       while (*p)
+                               if (!isdigit(*(p++)))
+                                       die(_("switch `C' expects a "
+                                             "numerical value"));
+               } else if (skip_prefix(option, "--whitespace=", &p)) {
+                       if (*p && strcmp(p, "warn") && strcmp(p, "nowarn") &&
+                           strcmp(p, "error") && strcmp(p, "error-all"))
+                               die("Invalid whitespace option: '%s'", p);
+               }
+       }
+
+       for (i = 0; i < exec.nr; i++)
+               if (check_exec_cmd(exec.items[i].string))
+                       exit(1);
+
        if (!(options.flags & REBASE_NO_QUIET))
-               strbuf_addstr(&options.git_am_opt, " -q");
+               argv_array_push(&options.git_am_opts, "-q");
+
+       if (options.keep_empty)
+               imply_interactive(&options, "--keep-empty");
+
+       if (gpg_sign) {
+               free(options.gpg_sign_opt);
+               options.gpg_sign_opt = xstrfmt("-S%s", gpg_sign);
+       }
+
+       if (exec.nr) {
+               int i;
+
+               imply_interactive(&options, "--exec");
+
+               strbuf_reset(&buf);
+               for (i = 0; i < exec.nr; i++)
+                       strbuf_addf(&buf, "exec %s\n", exec.items[i].string);
+               options.cmd = xstrdup(buf.buf);
+       }
+
+       if (rebase_merges) {
+               if (!*rebase_merges)
+                       ; /* default mode; do nothing */
+               else if (!strcmp("rebase-cousins", rebase_merges))
+                       options.rebase_cousins = 1;
+               else if (strcmp("no-rebase-cousins", rebase_merges))
+                       die(_("Unknown mode: %s"), rebase_merges);
+               options.rebase_merges = 1;
+               imply_interactive(&options, "--rebase-merges");
+       }
+
+       if (strategy_options.nr) {
+               int i;
+
+               if (!options.strategy)
+                       options.strategy = "recursive";
+
+               strbuf_reset(&buf);
+               for (i = 0; i < strategy_options.nr; i++)
+                       strbuf_addf(&buf, " --%s",
+                                   strategy_options.items[i].string);
+               options.strategy_opts = xstrdup(buf.buf);
+       }
+
+       if (options.strategy) {
+               options.strategy = xstrdup(options.strategy);
+               switch (options.type) {
+               case REBASE_AM:
+                       die(_("--strategy requires --merge or --interactive"));
+               case REBASE_MERGE:
+               case REBASE_INTERACTIVE:
+               case REBASE_PRESERVE_MERGES:
+                       /* compatible */
+                       break;
+               case REBASE_UNSPECIFIED:
+                       options.type = REBASE_MERGE;
+                       break;
+               default:
+                       BUG("unhandled rebase type (%d)", options.type);
+               }
+       }
+
+       if (options.type == REBASE_MERGE)
+               imply_interactive(&options, "--merge");
+
+       if (options.root && !options.onto_name)
+               imply_interactive(&options, "--root without --onto");
+
+       if (isatty(2) && options.flags & REBASE_NO_QUIET)
+               strbuf_addstr(&options.git_format_patch_opt, " --progress");
 
        switch (options.type) {
        case REBASE_MERGE:
@@ -474,10 +1793,67 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                break;
        }
 
+       if (reschedule_failed_exec > 0 && !is_interactive(&options))
+               die(_("--reschedule-failed-exec requires "
+                     "--exec or --interactive"));
+       if (reschedule_failed_exec >= 0)
+               options.reschedule_failed_exec = reschedule_failed_exec;
+
+       if (options.git_am_opts.argc) {
+               /* all am options except -q are compatible only with --am */
+               for (i = options.git_am_opts.argc - 1; i >= 0; i--)
+                       if (strcmp(options.git_am_opts.argv[i], "-q"))
+                               break;
+
+               if (is_interactive(&options) && i >= 0)
+                       die(_("cannot combine am options with either "
+                             "interactive or merge options"));
+       }
+
+       if (options.signoff) {
+               if (options.type == REBASE_PRESERVE_MERGES)
+                       die("cannot combine '--signoff' with "
+                           "'--preserve-merges'");
+               argv_array_push(&options.git_am_opts, "--signoff");
+               options.flags |= REBASE_FORCE;
+       }
+
+       if (options.type == REBASE_PRESERVE_MERGES) {
+               /*
+                * Note: incompatibility with --signoff handled in signoff block above
+                * Note: incompatibility with --interactive is just a strong warning;
+                *       git-rebase.txt caveats with "unless you know what you are doing"
+                */
+               if (options.rebase_merges)
+                       die(_("cannot combine '--preserve-merges' with "
+                             "'--rebase-merges'"));
+
+               if (options.reschedule_failed_exec)
+                       die(_("error: cannot combine '--preserve-merges' with "
+                             "'--reschedule-failed-exec'"));
+       }
+
+       if (options.rebase_merges) {
+               if (strategy_options.nr)
+                       die(_("cannot combine '--rebase-merges' with "
+                             "'--strategy-option'"));
+               if (options.strategy)
+                       die(_("cannot combine '--rebase-merges' with "
+                             "'--strategy'"));
+       }
+
        if (!options.root) {
-               if (argc < 1)
-                       die("TODO: handle @{upstream}");
-               else {
+               if (argc < 1) {
+                       struct branch *branch;
+
+                       branch = branch_get(NULL);
+                       options.upstream_name = branch_get_upstream(branch,
+                                                                   NULL);
+                       if (!options.upstream_name)
+                               error_on_missing_default_upstream();
+                       if (fork_point < 0)
+                               fork_point = 1;
+               } else {
                        options.upstream_name = argv[0];
                        argc--;
                        argv++;
@@ -488,8 +1864,22 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                if (!options.upstream)
                        die(_("invalid upstream '%s'"), options.upstream_name);
                options.upstream_arg = options.upstream_name;
-       } else
-               die("TODO: upstream for --root");
+       } else {
+               if (!options.onto_name) {
+                       if (commit_tree("", 0, the_hash_algo->empty_tree, NULL,
+                                       &squash_onto, NULL, NULL) < 0)
+                               die(_("Could not create new root commit"));
+                       options.squash_onto = &squash_onto;
+                       options.onto_name = squash_onto_name =
+                               xstrdup(oid_to_hex(&squash_onto));
+               }
+               options.upstream_name = NULL;
+               options.upstream = NULL;
+               if (argc > 1)
+                       usage_with_options(builtin_rebase_usage,
+                                          builtin_rebase_options);
+               options.upstream_arg = "--root";
+       }
 
        /* Make sure the branch to rebase onto is valid. */
        if (!options.onto_name)
@@ -512,11 +1902,25 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
         * branch_name -- branch/commit being rebased, or
         *                HEAD (already detached)
         * orig_head -- commit object name of tip of the branch before rebasing
-        * head_name -- refs/heads/<that-branch> or "detached HEAD"
+        * head_name -- refs/heads/<that-branch> or NULL (detached HEAD)
         */
-       if (argc > 0)
-                die("TODO: handle switch_to");
-       else {
+       if (argc == 1) {
+               /* Is it "rebase other branchname" or "rebase other commit"? */
+               branch_name = argv[0];
+               options.switch_to = argv[0];
+
+               /* Is it a local branch? */
+               strbuf_reset(&buf);
+               strbuf_addf(&buf, "refs/heads/%s", branch_name);
+               if (!read_ref(buf.buf, &options.orig_head))
+                       options.head_name = xstrdup(buf.buf);
+               /* If not is it a valid ref (branch or commit)? */
+               else if (!get_oid(branch_name, &options.orig_head))
+                       options.head_name = NULL;
+               else
+                       die(_("fatal: no such branch/commit '%s'"),
+                           branch_name);
+       } else if (argc == 0) {
                /* Do not need to switch branches, we are already on it. */
                options.head_name =
                        xstrdup_or_null(resolve_ref_unsafe("HEAD", 0, NULL,
@@ -529,17 +1933,83 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                                branch_name = options.head_name;
 
                } else {
-                       options.head_name = xstrdup("detached HEAD");
+                       FREE_AND_NULL(options.head_name);
                        branch_name = "HEAD";
                }
                if (get_oid("HEAD", &options.orig_head))
                        die(_("Could not resolve HEAD to a revision"));
+       } else
+               BUG("unexpected number of arguments left to parse");
+
+       if (fork_point > 0) {
+               struct commit *head =
+                       lookup_commit_reference(the_repository,
+                                               &options.orig_head);
+               options.restrict_revision =
+                       get_fork_point(options.upstream_name, head);
        }
 
-       if (read_index(the_repository->index) < 0)
+       if (repo_read_index(the_repository) < 0)
                die(_("could not read index"));
 
-       if (require_clean_work_tree("rebase",
+       if (options.autostash) {
+               struct lock_file lock_file = LOCK_INIT;
+               int fd;
+
+               fd = hold_locked_index(&lock_file, 0);
+               refresh_cache(REFRESH_QUIET);
+               if (0 <= fd)
+                       repo_update_index_if_able(the_repository, &lock_file);
+               rollback_lock_file(&lock_file);
+
+               if (has_unstaged_changes(the_repository, 1) ||
+                   has_uncommitted_changes(the_repository, 1)) {
+                       const char *autostash =
+                               state_dir_path("autostash", &options);
+                       struct child_process stash = CHILD_PROCESS_INIT;
+                       struct object_id oid;
+                       struct commit *head =
+                               lookup_commit_reference(the_repository,
+                                                       &options.orig_head);
+
+                       argv_array_pushl(&stash.args,
+                                        "stash", "create", "autostash", NULL);
+                       stash.git_cmd = 1;
+                       stash.no_stdin = 1;
+                       strbuf_reset(&buf);
+                       if (capture_command(&stash, &buf, GIT_MAX_HEXSZ))
+                               die(_("Cannot autostash"));
+                       strbuf_trim_trailing_newline(&buf);
+                       if (get_oid(buf.buf, &oid))
+                               die(_("Unexpected stash response: '%s'"),
+                                   buf.buf);
+                       strbuf_reset(&buf);
+                       strbuf_add_unique_abbrev(&buf, &oid, DEFAULT_ABBREV);
+
+                       if (safe_create_leading_directories_const(autostash))
+                               die(_("Could not create directory for '%s'"),
+                                   options.state_dir);
+                       write_file(autostash, "%s", oid_to_hex(&oid));
+                       printf(_("Created autostash: %s\n"), buf.buf);
+                       if (reset_head(&head->object.oid, "reset --hard",
+                                      NULL, RESET_HEAD_HARD, NULL, NULL) < 0)
+                               die(_("could not reset --hard"));
+                       printf(_("HEAD is now at %s"),
+                              find_unique_abbrev(&head->object.oid,
+                                                 DEFAULT_ABBREV));
+                       strbuf_reset(&buf);
+                       pp_commit_easy(CMIT_FMT_ONELINE, head, &buf);
+                       if (buf.len > 0)
+                               printf(" %s", buf.buf);
+                       putchar('\n');
+
+                       if (discard_index(the_repository->index) < 0 ||
+                               repo_read_index(the_repository) < 0)
+                               die(_("could not read index"));
+               }
+       }
+
+       if (require_clean_work_tree(the_repository, "rebase",
                                    _("Please commit or stash them."), 1, 1)) {
                ret = 1;
                goto cleanup;
@@ -557,10 +2027,36 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
         */
        if (can_fast_forward(options.onto, &options.orig_head, &merge_base) &&
            !is_interactive(&options) && !options.restrict_revision &&
+           options.upstream &&
            !oidcmp(&options.upstream->object.oid, &options.onto->object.oid)) {
                int flag;
 
                if (!(options.flags & REBASE_FORCE)) {
+                       /* Lazily switch to the target branch if needed... */
+                       if (options.switch_to) {
+                               struct object_id oid;
+
+                               if (get_oid(options.switch_to, &oid) < 0) {
+                                       ret = !!error(_("could not parse '%s'"),
+                                                     options.switch_to);
+                                       goto cleanup;
+                               }
+
+                               strbuf_reset(&buf);
+                               strbuf_addf(&buf, "%s: checkout %s",
+                                           getenv(GIT_REFLOG_ACTION_ENVIRONMENT),
+                                           options.switch_to);
+                               if (reset_head(&oid, "checkout",
+                                              options.head_name,
+                                              RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
+                                              NULL, buf.buf) < 0) {
+                                       ret = !!error(_("could not switch to "
+                                                       "%s"),
+                                                     options.switch_to);
+                                       goto cleanup;
+                               }
+                       }
+
                        if (!(options.flags & REBASE_NO_QUIET))
                                ; /* be quiet */
                        else if (!strcmp(branch_name, "HEAD") &&
@@ -590,10 +2086,15 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
        if (options.flags & REBASE_DIFFSTAT) {
                struct diff_options opts;
 
-               if (options.flags & REBASE_VERBOSE)
-                       printf(_("Changes from %s to %s:\n"),
-                               oid_to_hex(&merge_base),
-                               oid_to_hex(&options.onto->object.oid));
+               if (options.flags & REBASE_VERBOSE) {
+                       if (is_null_oid(&merge_base))
+                               printf(_("Changes to %s:\n"),
+                                      oid_to_hex(&options.onto->object.oid));
+                       else
+                               printf(_("Changes from %s to %s:\n"),
+                                      oid_to_hex(&merge_base),
+                                      oid_to_hex(&options.onto->object.oid));
+               }
 
                /* We want color (if set), but no pager */
                diff_setup(&opts);
@@ -603,22 +2104,48 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
                opts.detect_rename = DIFF_DETECT_RENAME;
                diff_setup_done(&opts);
-               diff_tree_oid(&merge_base, &options.onto->object.oid,
-                             "", &opts);
+               diff_tree_oid(is_null_oid(&merge_base) ?
+                             the_hash_algo->empty_tree : &merge_base,
+                             &options.onto->object.oid, "", &opts);
                diffcore_std(&opts);
                diff_flush(&opts);
        }
 
+       if (is_interactive(&options))
+               goto run_rebase;
+
        /* Detach HEAD and reset the tree */
        if (options.flags & REBASE_NO_QUIET)
                printf(_("First, rewinding head to replay your work on top of "
                         "it...\n"));
 
-       strbuf_addf(&msg, "rebase: checkout %s", options.onto_name);
-       if (reset_head(&options.onto->object.oid, "checkout", NULL, 1))
+       strbuf_addf(&msg, "%s: checkout %s",
+                   getenv(GIT_REFLOG_ACTION_ENVIRONMENT), options.onto_name);
+       if (reset_head(&options.onto->object.oid, "checkout", NULL,
+                      RESET_HEAD_DETACH | RESET_ORIG_HEAD |
+                      RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
+                      NULL, msg.buf))
                die(_("Could not detach HEAD"));
        strbuf_release(&msg);
 
+       /*
+        * If the onto is a proper descendant of the tip of the branch, then
+        * we just fast-forwarded.
+        */
+       strbuf_reset(&msg);
+       if (oideq(&merge_base, &options.orig_head)) {
+               printf(_("Fast-forwarded %s to %s.\n"),
+                       branch_name, options.onto_name);
+               strbuf_addf(&msg, "rebase finished: %s onto %s",
+                       options.head_name ? options.head_name : "detached HEAD",
+                       oid_to_hex(&options.onto->object.oid));
+               reset_head(NULL, "Fast-forwarded", options.head_name,
+                          RESET_HEAD_REFS_ONLY, "HEAD", msg.buf);
+               strbuf_release(&msg);
+               ret = !!finish_rebase(&options);
+               goto cleanup;
+       }
+
        strbuf_addf(&revisions, "%s..%s",
                    options.root ? oid_to_hex(&options.onto->object.oid) :
                    (options.restrict_revision ?
@@ -628,10 +2155,15 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
        options.revisions = revisions.buf;
 
-       ret = !!run_specific_rebase(&options);
+run_rebase:
+       ret = !!run_specific_rebase(&options, action);
 
 cleanup:
+       strbuf_release(&buf);
        strbuf_release(&revisions);
        free(options.head_name);
+       free(options.gpg_sign_opt);
+       free(options.cmd);
+       free(squash_onto_name);
        return ret;
 }