/*
 * "git rebase" builtin command
 *
 * Copyright (c) 2018 Pratik Karki
 */

#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "builtin.h"
#include "run-command.h"
#include "exec-cmd.h"
#include "argv-array.h"
#include "dir.h"
#include "packfile.h"
#include "refs.h"
#include "quote.h"
#include "config.h"
#include "cache-tree.h"
#include "unpack-trees.h"
#include "lockfile.h"
#include "parse-options.h"
#include "commit.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>] "
                "[<upstream>] [<branch>]"),
        N_("git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] "
                "--root [<branch>]"),
        N_("git rebase --continue | --abort | --skip | --edit-todo"),
        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")

enum rebase_type {
        REBASE_UNSPECIFIED = -1,
        REBASE_AM,
        REBASE_MERGE,
        REBASE_INTERACTIVE,
        REBASE_PRESERVE_MERGES
};

struct rebase_options {
        enum rebase_type type;
        const char *state_dir;
        struct commit *upstream;
        const char *upstream_name;
        const char *upstream_arg;
        char *head_name;
        struct object_id orig_head;
        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 {
                REBASE_NO_QUIET = 1<<0,
                REBASE_VERBOSE = 1<<1,
                REBASE_DIFFSTAT = 1<<2,
                REBASE_FORCE = 1<<3,
                REBASE_INTERACTIVE_EXPLICIT = 1<<4,
        } flags;
        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;
};

#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->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 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;
        unsigned flags = 0;
        int abbreviate_commands = 0, ret = 0;
        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;

        git_config_get_bool("rebase.abbreviatecommands", &abbreviate_commands);

        if (argc == 1)
                usage_with_options(builtin_rebase_interactive_usage, options);

        argc = parse_options(argc, argv, NULL, options,
                        builtin_rebase_interactive_usage, PARSE_OPT_KEEP_ARGV0);

        if (!is_null_oid(&squash_onto))
                opts.squash_onto = &squash_onto;

        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;

        if (opts.rebase_cousins >= 0 && !opts.rebase_merges)
                warning(_("--[no-]rebase-cousins has no effect without "
                          "--rebase-merges"));

        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 int use_builtin_rebase(void)
{
        struct child_process cp = CHILD_PROCESS_INIT;
        struct strbuf out = STRBUF_INIT;
        int ret, env = git_env_bool("GIT_TEST_REBASE_USE_BUILTIN", -1);

        if (env != -1)
                return env;

        argv_array_pushl(&cp.args,
                         "config", "--bool", "rebase.usebuiltin", NULL);
        cp.git_cmd = 1;
        if (capture_command(&cp, &out, 6)) {
                strbuf_release(&out);
                return 1;
        }

        strbuf_trim(&out);
        ret = !strcmp("true", out.buf);
        strbuf_release(&out);
        return ret;
}

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)
{
        static struct strbuf path = STRBUF_INIT;
        static size_t prefix_len;

        if (!prefix_len) {
                strbuf_addf(&path, "%s/", opts->state_dir);
                prefix_len = path.len;
        }

        strbuf_setlen(&path, prefix_len);
        strbuf_addstr(&path, filename);
        return path.buf;
}

/* 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 };

        delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
        apply_autostash(opts);
        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);

        return 0;
}

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)

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;
        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(&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(&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 (!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_orig_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 orig_head_reflog = STRBUF_INIT, head_reflog = STRBUF_INIT;
        int ret;

        if (!opts->head_name)
                return 0; /* nothing to move back to */

        if (!opts->onto)
                BUG("move_to_original_branch without onto");

        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);

        strbuf_release(&orig_head_reflog);
        strbuf_release(&head_reflog);
        return ret;
}

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)
{
        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)
{
        const char *argv[] = { NULL, NULL };
        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 */
                struct child_process child = CHILD_PROCESS_INIT;

                argv_array_pushf(&child.env_array, "GIT_CHERRY_PICK_HELP=%s",
                                 resolvemsg);
                if (!(opts->flags & REBASE_INTERACTIVE_EXPLICIT)) {
                        argv_array_push(&child.env_array,
                                        "GIT_SEQUENCE_EDITOR=:");
                        opts->autosquash = 0;
                }

                child.git_cmd = 1;
                argv_array_push(&child.args, "rebase--interactive");

                if (opts->action)
                        argv_array_pushf(&child.args, "--%s", opts->action);
                if (opts->keep_empty)
                        argv_array_push(&child.args, "--keep-empty");
                if (opts->rebase_merges)
                        argv_array_push(&child.args, "--rebase-merges");
                if (opts->rebase_cousins)
                        argv_array_push(&child.args, "--rebase-cousins");
                if (opts->autosquash)
                        argv_array_push(&child.args, "--autosquash");
                if (opts->flags & REBASE_VERBOSE)
                        argv_array_push(&child.args, "--verbose");
                if (opts->flags & REBASE_FORCE)
                        argv_array_push(&child.args, "--no-ff");
                if (opts->restrict_revision)
                        argv_array_pushf(&child.args,
                                         "--restrict-revision=^%s",
                                         oid_to_hex(&opts->restrict_revision->object.oid));
                if (opts->upstream)
                        argv_array_pushf(&child.args, "--upstream=%s",
                                         oid_to_hex(&opts->upstream->object.oid));
                if (opts->onto)
                        argv_array_pushf(&child.args, "--onto=%s",
                                         oid_to_hex(&opts->onto->object.oid));
                if (opts->squash_onto)
                        argv_array_pushf(&child.args, "--squash-onto=%s",
                                         oid_to_hex(opts->squash_onto));
                if (opts->onto_name)
                        argv_array_pushf(&child.args, "--onto-name=%s",
                                         opts->onto_name);
                argv_array_pushf(&child.args, "--head-name=%s",
                                 opts->head_name ?
                                 opts->head_name : "detached HEAD");
                if (opts->strategy)
                        argv_array_pushf(&child.args, "--strategy=%s",
                                         opts->strategy);
                if (opts->strategy_opts)
                        argv_array_pushf(&child.args, "--strategy-opts=%s",
                                         opts->strategy_opts);
                if (opts->switch_to)
                        argv_array_pushf(&child.args, "--switch-to=%s",
                                         opts->switch_to);
                if (opts->cmd)
                        argv_array_pushf(&child.args, "--cmd=%s", opts->cmd);
                if (opts->allow_empty_message)
                        argv_array_push(&child.args, "--allow-empty-message");
                if (opts->allow_rerere_autoupdate == RERERE_AUTOUPDATE)
                        argv_array_push(&child.args, "--rerere-autoupdate");
                else if (opts->allow_rerere_autoupdate == RERERE_NOAUTOUPDATE)
                        argv_array_push(&child.args, "--no-rerere-autoupdate");
                if (opts->gpg_sign_opt)
                        argv_array_push(&child.args, opts->gpg_sign_opt);
                if (opts->signoff)
                        argv_array_push(&child.args, "--signoff");
                if (opts->reschedule_failed_exec)
                        argv_array_push(&child.args, "--reschedule-failed-exec");

                status = run_command(&child);
                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", 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", 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");
        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_PRESERVE_MERGES:
                backend = "git-rebase--preserve-merges";
                backend_func = "git_rebase__preserve_merges";
                break;
        default:
                BUG("Unhandled rebase type %d", opts->type);
                break;
        }

        strbuf_addf(&script_snippet,
                    ". git-sh-setup && . git-rebase--common &&"
                    " . %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(opts);
                strbuf_addstr(&dir, opts->state_dir);
                remove_dir_recursively(&dir, 0);
                strbuf_release(&dir);
                die("Nothing to do");
        }

        strbuf_release(&script_snippet);

        return status ? -1 : 0;
}

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;
                return 0;
        }

        if (!strcmp(var, "rebase.autosquash")) {
                opts->autosquash = git_config_bool(var, value);
                return 0;
        }

        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 (!strcmp(var, "rebase.autostash")) {
                opts->autostash = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "rebase.reschedulefailedexec")) {
                opts->reschedule_failed_exec = git_config_bool(var, value);
                return 0;
        }

        return git_default_config(var, value, data);
}

/*
 * Determines whether the commits in from..to are linear, i.e. contain
 * no merge commits. This function *expects* `from` to be an ancestor of
 * `to`.
 */
static int is_linear_history(struct commit *from, struct commit *to)
{
        while (to && to != from) {
                parse_commit(to);
                if (!to->parents)
                        return 1;
                if (to->parents->next)
                        return 0;
                to = to->parents->item;
        }
        return 1;
}

static int can_fast_forward(struct commit *onto, struct object_id *head_oid,
                            struct object_id *merge_base)
{
        struct commit *head = lookup_commit(the_repository, head_oid);
        struct commit_list *merge_bases;
        int res;

        if (!head)
                return 0;

        merge_bases = get_merge_bases(onto, head);
        if (merge_bases && !merge_bases->next) {
                oidcpy(merge_base, &merge_bases->item->object.oid);
                res = oideq(merge_base, &onto->object.oid);
        } else {
                oidcpy(merge_base, &null_oid);
                res = 0;
        }
        free_commit_list(merge_bases);
        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 = REBASE_OPTIONS_INIT;
        const char *branch_name;
        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;
        struct option builtin_rebase_options[] = {
                OPT_STRING(0, "onto", &options.onto_name,
                           N_("revision"),
                           N_("rebase onto given branch instead of upstream")),
                OPT_BOOL(0, "no-verify", &ok_to_skip_pre_rebase,
                         N_("allow pre-rebase hook to run")),
                OPT_NEGBIT('q', "quiet", &options.flags,
                           N_("be quiet. implies --no-stat"),
                           REBASE_NO_QUIET| REBASE_VERBOSE | REBASE_DIFFSTAT),
                OPT_BIT('v', "verbose", &options.flags,
                        N_("display a diffstat of what changed upstream"),
                        REBASE_NO_QUIET | REBASE_VERBOSE | REBASE_DIFFSTAT),
                {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_("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",
                         &options.reschedule_failed_exec,
                         N_("automatically re-schedule any `exec` that fails")),
                OPT_END(),
        };
        int i;

        /*
         * 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???");
        }

        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);

        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 (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);
                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);
                ret = finish_rebase(&options);
                goto cleanup;
        }
        case ACTION_QUIT: {
                strbuf_reset(&buf);
                strbuf_addstr(&buf, options.state_dir);
                ret = !!remove_dir_recursively(&buf, 0);
                if (ret)
                        die(_("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))
                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:
        case REBASE_INTERACTIVE:
        case REBASE_PRESERVE_MERGES:
                options.state_dir = merge_dir();
                break;
        case REBASE_AM:
                options.state_dir = apply_dir();
                break;
        default:
                /* the default rebase backend is `--am` */
                options.type = REBASE_AM;
                options.state_dir = apply_dir();
                break;
        }

        if (options.reschedule_failed_exec && !is_interactive(&options))
                die(_("%s requires an interactive rebase"), "--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) {
                        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++;
                        if (!strcmp(options.upstream_name, "-"))
                                options.upstream_name = "@{-1}";
                }
                options.upstream = peel_committish(options.upstream_name);
                if (!options.upstream)
                        die(_("invalid upstream '%s'"), options.upstream_name);
                options.upstream_arg = options.upstream_name;
        } 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)
                options.onto_name = options.upstream_name;
        if (strstr(options.onto_name, "...")) {
                if (get_oid_mb(options.onto_name, &merge_base) < 0)
                        die(_("'%s': need exactly one merge base"),
                            options.onto_name);
                options.onto = lookup_commit_or_die(&merge_base,
                                                    options.onto_name);
        } else {
                options.onto = peel_committish(options.onto_name);
                if (!options.onto)
                        die(_("Does not point to a valid commit '%s'"),
                                options.onto_name);
        }

        /*
         * If the branch to rebase is given, that is the branch we will rebase
         * 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 NULL (detached HEAD)
         */
        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,
                                         &flags));
                if (!options.head_name)
                        die(_("No such ref: %s"), "HEAD");
                if (flags & REF_ISSYMREF) {
                        if (!skip_prefix(options.head_name,
                                         "refs/heads/", &branch_name))
                                branch_name = options.head_name;

                } else {
                        free(options.head_name);
                        options.head_name = NULL;
                        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 (repo_read_index(the_repository) < 0)
                die(_("could not read index"));

        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;
        }

        /*
         * Now we are rebasing commits upstream..orig_head (or with --root,
         * everything leading up to orig_head) on top of onto.
         */

        /*
         * Check if we are already based on onto with linear history,
         * but this should be done only when upstream and onto are the same
         * and if this is not an interactive rebase.
         */
        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") &&
                                 resolve_ref_unsafe("HEAD", 0, NULL, &flag))
                                puts(_("HEAD is up to date."));
                        else
                                printf(_("Current branch %s is up to date.\n"),
                                       branch_name);
                        ret = !!finish_rebase(&options);
                        goto cleanup;
                } else if (!(options.flags & REBASE_NO_QUIET))
                        ; /* be quiet */
                else if (!strcmp(branch_name, "HEAD") &&
                         resolve_ref_unsafe("HEAD", 0, NULL, &flag))
                        puts(_("HEAD is up to date, rebase forced."));
                else
                        printf(_("Current branch %s is up to date, rebase "
                                 "forced.\n"), branch_name);
        }

        /* If a hook exists, give it a chance to interrupt*/
        if (!ok_to_skip_pre_rebase &&
            run_hook_le(NULL, "pre-rebase", options.upstream_arg,
                        argc ? argv[0] : NULL, NULL))
                die(_("The pre-rebase hook refused to rebase."));

        if (options.flags & REBASE_DIFFSTAT) {
                struct diff_options opts;

                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);
                opts.stat_width = -1; /* use full terminal width */
                opts.stat_graph_width = -1; /* respect statGraphWidth config */
                opts.output_format |=
                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
                opts.detect_rename = DIFF_DETECT_RENAME;
                diff_setup_done(&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, "%s: checkout %s",
                    getenv(GIT_REFLOG_ACTION_ENVIRONMENT), options.onto_name);
        if (reset_head(&options.onto->object.oid, "checkout", NULL,
                       RESET_HEAD_DETACH | 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 (!oidcmp(&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, 0,
                           "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 ?
                     oid_to_hex(&options.restrict_revision->object.oid) :
                     oid_to_hex(&options.upstream->object.oid)),
                    oid_to_hex(&options.orig_head));

        options.revisions = revisions.buf;

run_rebase:
        ret = !!run_specific_rebase(&options);

cleanup:
        strbuf_release(&revisions);
        free(options.head_name);
        free(options.gpg_sign_opt);
        free(options.cmd);
        free(squash_onto_name);
        return ret;
}