Merge branch 'js/rebase-p-tests'
[gitweb.git] / builtin / rebase.c
index c44addb2a4c609af6e8bcbd47b3dd47768b4101a..0ee06aa3631ee89761d570b433994cc77302742e 100644 (file)
@@ -9,6 +9,40 @@
 #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"
+
+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(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
+};
 
 static int use_builtin_rebase(void)
 {
@@ -21,7 +55,7 @@ static int use_builtin_rebase(void)
        cp.git_cmd = 1;
        if (capture_command(&cp, &out, 6)) {
                strbuf_release(&out);
-               return 0;
+               return 1;
        }
 
        strbuf_trim(&out);
@@ -30,8 +64,827 @@ static int use_builtin_rebase(void)
        return ret;
 }
 
+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 strbuf git_am_opt;
+       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;
+};
+
+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 silently *upgrade* --merge to --interactive if needed */
+       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);
+
+       strbuf_reset(&buf);
+       if (read_one(state_dir_path("quiet", opts), &buf))
+               return -1;
+       if (buf.len)
+               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 = 1;
+               else if (!strcmp(buf.buf, "--no-rerere-autoupdate"))
+                       opts->allow_rerere_autoupdate = 0;
+               else
+                       warning(_("ignoring invalid allow_rerere_autoupdate: "
+                                 "'%s'"), buf.buf);
+       } else
+               opts->allow_rerere_autoupdate = -1;
+
+       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 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, "; ");
+       }
+}
+
+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_specific_rebase(struct rebase_options *opts)
+{
+       const char *argv[] = { NULL, NULL };
+       struct strbuf script_snippet = 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_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 > 0)
+                       argv_array_push(&child.args, "--rerere-autoupdate");
+               else if (opts->allow_rerere_autoupdate == 0)
+                       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");
+
+               status = run_command(&child);
+               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");
+       add_var(&script_snippet, "git_am_opt", opts->git_am_opt.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 < 0 ? "" :
+               opts->allow_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_EDITOR=:; export GIT_EDITOR; ");
+               opts->autosquash = 0;
+       }
+
+       switch (opts->type) {
+       case REBASE_AM:
+               backend = "git-rebase--am";
+               backend_func = "git_rebase__am";
+               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";
+               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;
+}
+
+#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,
+                     const char *reflog_orig_head, const char *reflog_head)
+{
+       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 (switch_to_branch && !starts_with(switch_to_branch, "refs/"))
+               BUG("Not a fully qualified branch: '%s'", switch_to_branch);
+
+       if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
+               return -1;
+
+       if (!oid) {
+               if (get_oid("HEAD", &head_oid)) {
+                       rollback_lock_file(&lock);
+                       return error(_("could not determine HEAD revision"));
+               }
+               oid = &head_oid;
+       }
+
+       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 (!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 (unpack_trees(1, &desc, &unpack_tree_opts)) {
+               rollback_lock_file(&lock);
+               free((void *)desc.buffer);
+               return -1;
+       }
+
+       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;
+               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, REF_NO_DEREF,
+                                UPDATE_REFS_MSG_ON_ERR);
+       else {
+               ret = create_symref("HEAD", switch_to_branch, msg.buf);
+               if (!ret)
+                       ret = update_ref(reflog_head, "HEAD", oid, NULL, 0,
+                                        UPDATE_REFS_MSG_ON_ERR);
+       }
+
+       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;
+               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;
+       }
+
+       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;
+
+       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;
+
+       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);
+}
+
 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,
+               .allow_rerere_autoupdate  = -1,
+               .allow_empty_message = 1,
+               .git_format_patch_opt = STRBUF_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 {
+               NO_ACTION,
+               ACTION_CONTINUE,
+               ACTION_SKIP,
+               ACTION_ABORT,
+               ACTION_QUIT,
+               ACTION_EDIT_TODO,
+               ACTION_SHOW_CURRENT_PATCH,
+       } action = NO_ACTION;
+       int committer_date_is_author_date = 0;
+       int ignore_date = 0;
+       int ignore_whitespace = 0;
+       const char *gpg_sign = NULL;
+       int opt_c = -1;
+       struct string_list whitespace = STRING_LIST_INIT_NODUP;
+       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, "ignore-whitespace", &ignore_whitespace,
+                        N_("passed to 'git apply'")),
+               OPT_BOOL(0, "signoff", &options.signoff,
+                        N_("add a Signed-off-by: line to each commit")),
+               OPT_BOOL(0, "committer-date-is-author-date",
+                        &committer_date_is_author_date,
+                        N_("passed to 'git am'")),
+               OPT_BOOL(0, "ignore-date", &ignore_date,
+                        N_("passed to 'git am'")),
+               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_BOOL(0, "rerere-autoupdate",
+                        &options.allow_rerere_autoupdate,
+                        N_("allow rerere to update index  with resolved "
+                           "conflict")),
+               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_STRING_LIST(0, "whitespace", &whitespace,
+                               N_("whitespace"), N_("passed to 'git apply'")),
+               OPT_SET_INT('C', NULL, &opt_c, N_("passed to 'git apply'"),
+                           REBASE_AM),
+               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_END(),
+       };
+
        /*
         * NEEDSWORK: Once the builtin rebase has been tested enough
         * and git-legacy-rebase.sh is retired to contrib/, this preamble
@@ -48,11 +901,645 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                        BUG("sane_execvp() returned???");
        }
 
-       if (argc != 2)
-               die(_("Usage: %s <base>"), argv[0]);
+       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();
 
-       die("TODO");
+       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 != NO_ACTION && 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 != NO_ACTION && !in_progress)
+               die(_("No rebase in progress?"));
+
+       if (action == ACTION_EDIT_TODO && !is_interactive(&options))
+               die(_("The --edit-todo action can only be used during "
+                     "interactive rebase."));
+
+       switch (action) {
+       case ACTION_CONTINUE: {
+               struct object_id head;
+               struct lock_file lock_file = LOCK_INIT;
+               int fd;
+
+               options.action = "continue";
+
+               /* Sanity check */
+               if (get_oid("HEAD", &head))
+                       die(_("Cannot read HEAD"));
+
+               fd = hold_locked_index(&lock_file, 0);
+               if (read_index(the_repository->index) < 0)
+                       die(_("could not read index"));
+               refresh_index(the_repository->index, REFRESH_QUIET, NULL, NULL,
+                             NULL);
+               if (0 <= fd)
+                       update_index_if_able(the_repository->index,
+                                            &lock_file);
+               rollback_lock_file(&lock_file);
+
+               if (has_unstaged_changes(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";
+
+               rerere_clear(&merge_rr);
+               string_list_clear(&merge_rr, 1);
+
+               if (reset_head(NULL, "reset", NULL, 0, NULL, NULL) < 0)
+                       die(_("could not discard worktree changes"));
+               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";
+
+               rerere_clear(&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, 0, NULL, NULL) < 0)
+                       die(_("could not move back to %s"),
+                           oid_to_hex(&options.orig_head));
+               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 NO_ACTION:
+               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);
+       }
+
+       if (!(options.flags & REBASE_NO_QUIET))
+               strbuf_addstr(&options.git_am_opt, " -q");
+
+       if (committer_date_is_author_date) {
+               strbuf_addstr(&options.git_am_opt,
+                             " --committer-date-is-author-date");
+               options.flags |= REBASE_FORCE;
+       }
+
+       if (ignore_whitespace)
+               strbuf_addstr(&options.git_am_opt, " --ignore-whitespace");
+
+       if (ignore_date) {
+               strbuf_addstr(&options.git_am_opt, " --ignore-date");
+               options.flags |= REBASE_FORCE;
+       }
+
+       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 (opt_c >= 0)
+               strbuf_addf(&options.git_am_opt, " -C%d", opt_c);
+
+       if (whitespace.nr) {
+               int i;
+
+               for (i = 0; i < whitespace.nr; i++) {
+                       const char *item = whitespace.items[i].string;
+
+                       strbuf_addf(&options.git_am_opt, " --whitespace=%s",
+                                   item);
+
+                       if ((!strcmp(item, "fix")) || (!strcmp(item, "strip")))
+                               options.flags |= REBASE_FORCE;
+               }
+       }
+
+       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.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.git_am_opt.len) {
+               const char *p;
+
+               /* all am options except -q are compatible only with --am */
+               strbuf_reset(&buf);
+               strbuf_addbuf(&buf, &options.git_am_opt);
+               strbuf_addch(&buf, ' ');
+               while ((p = strstr(buf.buf, " -q ")))
+                       strbuf_splice(&buf, p - buf.buf, 4, " ", 1);
+               strbuf_trim(&buf);
+
+               if (is_interactive(&options) && buf.len)
+                       die(_("error: cannot combine interactive options "
+                             "(--interactive, --exec, --rebase-merges, "
+                             "--preserve-merges, --keep-empty, --root + "
+                             "--onto) with am options (%s)"), buf.buf);
+               if (options.type == REBASE_MERGE && buf.len)
+                       die(_("error: cannot combine merge options (--merge, "
+                             "--strategy, --strategy-option) with am options "
+                             "(%s)"), buf.buf);
+       }
+
+       if (options.signoff) {
+               if (options.type == REBASE_PRESERVE_MERGES)
+                       die("cannot combine '--signoff' with "
+                           "'--preserve-merges'");
+               strbuf_addstr(&options.git_am_opt, " --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(_("error: cannot combine '--preserve-merges' with "
+                             "'--rebase-merges'"));
+
+       if (options.rebase_merges) {
+               if (strategy_options.nr)
+                       die(_("error: cannot combine '--rebase-merges' with "
+                             "'--strategy-option'"));
+               if (options.strategy)
+                       die(_("error: 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 (read_index(the_repository->index) < 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)
+                       update_index_if_able(&the_index, &lock_file);
+               rollback_lock_file(&lock_file);
+
+               if (has_unstaged_changes(1) || has_uncommitted_changes(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, 0, 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 ||
+                               read_index(the_repository->index) < 0)
+                               die(_("could not read index"));
+               }
+       }
+
+       if (require_clean_work_tree("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, "rebase: checkout %s",
+                                           options.switch_to);
+                               if (reset_head(&oid, "checkout",
+                                              options.head_name, 0,
+                                              NULL, NULL) < 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)
+                       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(&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,
+           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;
 }