Merge branch 'pw/use-in-process-checkout-in-rebase'

Use an internal call to reset_head() helper function instead of
spawning "git checkout" in "rebase", and update code paths that are
involved in the change.

* pw/use-in-process-checkout-in-rebase:
  rebase -m: don't fork git checkout
  rebase --apply: set ORIG_HEAD correctly
  rebase --apply: fix reflog
  reset_head(): take struct rebase_head_opts
  rebase: cleanup reset_head() calls
  create_autostash(): remove unneeded parameter
  reset_head(): make default_reflog_action optional
  reset_head(): factor out ref updates
  reset_head(): remove action parameter
  rebase --apply: don't run post-checkout hook if there is an error
  rebase: do not remove untracked files on checkout
  rebase: pass correct arguments to post-checkout hook
  t5403: refactor rebase post-checkout hook tests
  rebase: factor out checkout for up to date branch

9 files changed, 312 insertions, 163 deletions

diff --git a/builtin/merge.c b/builtin/merge.c
index 133831d42f..a94a03384a 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1568,8 +1568,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 		if (autostash)
 			create_autostash(the_repository,
-					 git_path_merge_autostash(the_repository),
-					 "merge");
+					 git_path_merge_autostash(the_repository));
 		if (checkout_fast_forward(the_repository,
 					  &head_commit->object.oid,
 					  &commit->object.oid,
@@ -1640,8 +1639,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	if (autostash)
 		create_autostash(the_repository,
-				 git_path_merge_autostash(the_repository),
-				 "merge");
+				 git_path_merge_autostash(the_repository));
 
 	/* We are going to make a new commit. */
 	git_committer_info(IDENT_STRICT);
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 2e6d8fa34e..d858add3fe 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -571,7 +571,8 @@ static int finish_rebase(struct rebase_options *opts)
 
 static int move_to_original_branch(struct rebase_options *opts)
 {
-	struct strbuf orig_head_reflog = STRBUF_INIT, head_reflog = STRBUF_INIT;
+	struct strbuf branch_reflog = STRBUF_INIT, head_reflog = STRBUF_INIT;
+	struct reset_head_opts ropts = { 0 };
 	int ret;
 
 	if (!opts->head_name)
@@ -580,16 +581,17 @@ static int move_to_original_branch(struct rebase_options *opts)
 	if (!opts->onto)
 		BUG("move_to_original_branch without onto");
 
-	strbuf_addf(&orig_head_reflog, "rebase finished: %s onto %s",
+	strbuf_addf(&branch_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(the_repository, NULL, "", opts->head_name,
-			 RESET_HEAD_REFS_ONLY,
-			 orig_head_reflog.buf, head_reflog.buf,
-			 DEFAULT_REFLOG_ACTION);
+	ropts.branch = opts->head_name;
+	ropts.flags = RESET_HEAD_REFS_ONLY;
+	ropts.branch_msg = branch_reflog.buf;
+	ropts.head_msg = head_reflog.buf;
+	ret = reset_head(the_repository, &ropts);
 
-	strbuf_release(&orig_head_reflog);
+	strbuf_release(&branch_reflog);
 	strbuf_release(&head_reflog);
 	return ret;
 }
@@ -671,13 +673,15 @@ static int run_am(struct rebase_options *opts)
 
 	status = run_command(&format_patch);
 	if (status) {
+		struct reset_head_opts ropts = { 0 };
 		unlink(rebased_patches);
 		free(rebased_patches);
 		strvec_clear(&am.args);
 
-		reset_head(the_repository, &opts->orig_head, "checkout",
-			   opts->head_name, 0,
-			   "HEAD", NULL, DEFAULT_REFLOG_ACTION);
+		ropts.oid = &opts->orig_head;
+		ropts.branch = opts->head_name;
+		ropts.default_reflog_action = DEFAULT_REFLOG_ACTION;
+		reset_head(the_repository, &ropts);
 		error(_("\ngit encountered an error while preparing the "
 			"patches to replay\n"
 			"these revisions:\n"
@@ -813,6 +817,26 @@ static int rebase_config(const char *var, const char *value, void *data)
 	return git_default_config(var, value, data);
 }
 
+static int checkout_up_to_date(struct rebase_options *options)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct reset_head_opts ropts = { 0 };
+	int ret = 0;
+
+	strbuf_addf(&buf, "%s: checkout %s",
+		    getenv(GIT_REFLOG_ACTION_ENVIRONMENT),
+		    options->switch_to);
+	ropts.oid = &options->orig_head;
+	ropts.branch = options->head_name;
+	ropts.flags = RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
+	ropts.head_msg = buf.buf;
+	if (reset_head(the_repository, &ropts) < 0)
+		ret = error(_("could not switch to %s"), options->switch_to);
+	strbuf_release(&buf);
+
+	return ret;
+}
+
 /*
  * Determines whether the commits in from..to are linear, i.e. contain
  * no merge commits. This function *expects* `from` to be an ancestor of
@@ -1018,6 +1042,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	int reschedule_failed_exec = -1;
 	int allow_preemptive_ff = 1;
 	int preserve_merges_selected = 0;
+	struct reset_head_opts ropts = { 0 };
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,
 			   N_("revision"),
@@ -1255,9 +1280,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 		rerere_clear(the_repository, &merge_rr);
 		string_list_clear(&merge_rr, 1);
-
-		if (reset_head(the_repository, NULL, "reset", NULL, RESET_HEAD_HARD,
-			       NULL, NULL, DEFAULT_REFLOG_ACTION) < 0)
+		ropts.flags = RESET_HEAD_HARD;
+		if (reset_head(the_repository, &ropts) < 0)
 			die(_("could not discard worktree changes"));
 		remove_branch_state(the_repository, 0);
 		if (read_basic_state(&options))
@@ -1274,9 +1298,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 		if (read_basic_state(&options))
 			exit(1);
-		if (reset_head(the_repository, &options.orig_head, "reset",
-			       options.head_name, RESET_HEAD_HARD,
-			       NULL, NULL, DEFAULT_REFLOG_ACTION) < 0)
+		ropts.oid = &options.orig_head;
+		ropts.branch = options.head_name;
+		ropts.flags = RESET_HEAD_HARD;
+		ropts.default_reflog_action = DEFAULT_REFLOG_ACTION;
+		if (reset_head(the_repository, &ropts) < 0)
 			die(_("could not move back to %s"),
 			    oid_to_hex(&options.orig_head));
 		remove_branch_state(the_repository, 0);
@@ -1642,10 +1668,10 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if (repo_read_index(the_repository) < 0)
 		die(_("could not read index"));
 
-	if (options.autostash) {
-		create_autostash(the_repository, state_dir_path("autostash", &options),
-				 DEFAULT_REFLOG_ACTION);
-	}
+	if (options.autostash)
+		create_autostash(the_repository,
+				 state_dir_path("autostash", &options));
+
 
 	if (require_clean_work_tree(the_repository, "rebase",
 				    _("Please commit or stash them."), 1, 1)) {
@@ -1674,21 +1700,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		if (!(options.flags & REBASE_FORCE)) {
 			/* Lazily switch to the target branch if needed... */
 			if (options.switch_to) {
-				strbuf_reset(&buf);
-				strbuf_addf(&buf, "%s: checkout %s",
-					    getenv(GIT_REFLOG_ACTION_ENVIRONMENT),
-					    options.switch_to);
-				if (reset_head(the_repository,
-					       &options.orig_head, "checkout",
-					       options.head_name,
-					       RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
-					       NULL, buf.buf,
-					       DEFAULT_REFLOG_ACTION) < 0) {
-					ret = error(_("could not switch to "
-							"%s"),
-						      options.switch_to);
+				ret = checkout_up_to_date(&options);
+				if (ret)
 					goto cleanup;
-				}
 			}
 
 			if (!(options.flags & REBASE_NO_QUIET))
@@ -1755,10 +1769,13 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	strbuf_addf(&msg, "%s: checkout %s",
 		    getenv(GIT_REFLOG_ACTION_ENVIRONMENT), options.onto_name);
-	if (reset_head(the_repository, &options.onto->object.oid, "checkout", NULL,
-		       RESET_HEAD_DETACH | RESET_ORIG_HEAD |
-		       RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
-		       NULL, msg.buf, DEFAULT_REFLOG_ACTION))
+	ropts.oid = &options.onto->object.oid;
+	ropts.orig_head = &options.orig_head,
+	ropts.flags = RESET_HEAD_DETACH | RESET_ORIG_HEAD |
+			RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
+	ropts.head_msg = msg.buf;
+	ropts.default_reflog_action = DEFAULT_REFLOG_ACTION;
+	if (reset_head(the_repository, &ropts))
 		die(_("Could not detach HEAD"));
 	strbuf_release(&msg);
 
@@ -1773,9 +1790,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		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(the_repository, NULL, "Fast-forwarded", options.head_name,
-			   RESET_HEAD_REFS_ONLY, "HEAD", msg.buf,
-			   DEFAULT_REFLOG_ACTION);
+		memset(&ropts, 0, sizeof(ropts));
+		ropts.branch = options.head_name;
+		ropts.flags = RESET_HEAD_REFS_ONLY;
+		ropts.head_msg = msg.buf;
+		reset_head(the_repository, &ropts);
 		strbuf_release(&msg);
 		ret = finish_rebase(&options);
 		goto cleanup;
diff --git a/reset.c b/reset.c
index 0881e63691..e3383a9334 100644
--- a/reset.c
+++ b/reset.c
@@ -9,37 +9,106 @@
 #include "unpack-trees.h"
 #include "hook.h"
 
-int reset_head(struct repository *r, struct object_id *oid, const char *action,
-	       const char *switch_to_branch, unsigned flags,
-	       const char *reflog_orig_head, const char *reflog_head,
-	       const char *default_reflog_action)
+static int update_refs(const struct reset_head_opts *opts,
+		       const struct object_id *oid,
+		       const struct object_id *head)
 {
-	unsigned detach_head = flags & RESET_HEAD_DETACH;
-	unsigned reset_hard = flags & RESET_HEAD_HARD;
-	unsigned run_hook = flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
-	unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
-	unsigned update_orig_head = flags & RESET_ORIG_HEAD;
-	struct object_id head_oid;
+	unsigned detach_head = opts->flags & RESET_HEAD_DETACH;
+	unsigned run_hook = opts->flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
+	unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
+	const struct object_id *orig_head = opts->orig_head;
+	const char *switch_to_branch = opts->branch;
+	const char *reflog_branch = opts->branch_msg;
+	const char *reflog_head = opts->head_msg;
+	const char *reflog_orig_head = opts->orig_head_msg;
+	const char *default_reflog_action = opts->default_reflog_action;
+	struct object_id *old_orig = NULL, oid_old_orig;
+	struct strbuf msg = STRBUF_INIT;
+	const char *reflog_action;
+	size_t prefix_len;
+	int ret;
+
+	if ((update_orig_head && !reflog_orig_head) || !reflog_head) {
+		if (!default_reflog_action)
+			BUG("default_reflog_action must be given when reflog messages are omitted");
+		reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
+		strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action :
+							  default_reflog_action);
+	}
+	prefix_len = msg.len;
+
+	if (update_orig_head) {
+		if (!get_oid("ORIG_HEAD", &oid_old_orig))
+			old_orig = &oid_old_orig;
+		if (head) {
+			if (!reflog_orig_head) {
+				strbuf_addstr(&msg, "updating ORIG_HEAD");
+				reflog_orig_head = msg.buf;
+			}
+			update_ref(reflog_orig_head, "ORIG_HEAD",
+				   orig_head ? orig_head : head,
+				   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, head,
+				 detach_head ? REF_NO_DEREF : 0,
+				 UPDATE_REFS_MSG_ON_ERR);
+	else {
+		ret = update_ref(reflog_branch ? reflog_branch : reflog_head,
+				 switch_to_branch, oid, NULL, 0,
+				 UPDATE_REFS_MSG_ON_ERR);
+		if (!ret)
+			ret = create_symref("HEAD", switch_to_branch,
+					    reflog_head);
+	}
+	if (!ret && run_hook)
+		run_hooks_l("post-checkout",
+			    oid_to_hex(head ? head : null_oid()),
+			    oid_to_hex(oid), "1", NULL);
+	strbuf_release(&msg);
+	return ret;
+}
+
+int reset_head(struct repository *r, const struct reset_head_opts *opts)
+{
+	const struct object_id *oid = opts->oid;
+	const char *switch_to_branch = opts->branch;
+	unsigned reset_hard = opts->flags & RESET_HEAD_HARD;
+	unsigned refs_only = opts->flags & RESET_HEAD_REFS_ONLY;
+	unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
+	struct object_id *head = NULL, head_oid;
 	struct tree_desc desc[2] = { { NULL }, { NULL } };
 	struct lock_file lock = LOCK_INIT;
 	struct unpack_trees_options unpack_tree_opts = { 0 };
 	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;
+	const char *action;
 	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 (opts->orig_head_msg && !update_orig_head)
+		BUG("ORIG_HEAD reflog message given without updating ORIG_HEAD");
+
+	if (opts->branch_msg && !opts->branch)
+		BUG("branch reflog message given without a branch");
+
 	if (!refs_only && repo_hold_locked_index(r, &lock, LOCK_REPORT_ON_ERROR) < 0) {
 		ret = -1;
 		goto leave_reset_head;
 	}
 
-	if ((!oid || !reset_hard) && get_oid("HEAD", &head_oid)) {
+	if (!get_oid("HEAD", &head_oid)) {
+		head = &head_oid;
+	} else if (!oid || !reset_hard) {
 		ret = error(_("could not determine HEAD revision"));
 		goto leave_reset_head;
 	}
@@ -48,8 +117,9 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
 		oid = &head_oid;
 
 	if (refs_only)
-		goto reset_head_refs;
+		return update_refs(opts, oid, head);
 
+	action = reset_hard ? "reset" : "checkout";
 	setup_unpack_trees_porcelain(&unpack_tree_opts, action);
 	unpack_tree_opts.head_idx = 1;
 	unpack_tree_opts.src_index = r->index;
@@ -59,7 +129,7 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
 	unpack_tree_opts.merge = 1;
 	unpack_tree_opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 	init_checkout_metadata(&unpack_tree_opts.meta, switch_to_branch, oid, NULL);
-	if (!detach_head)
+	if (reset_hard)
 		unpack_tree_opts.reset = UNPACK_RESET_PROTECT_UNTRACKED;
 
 	if (repo_read_index_unmerged(r) < 0) {
@@ -91,49 +161,10 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
 		goto leave_reset_head;
 	}
 
-reset_head_refs:
-	reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
-	strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : default_reflog_action);
-	prefix_len = msg.len;
-
-	if (update_orig_head) {
-		if (!get_oid("ORIG_HEAD", &oid_old_orig))
-			old_orig = &oid_old_orig;
-		if (!get_oid("HEAD", &oid_orig)) {
-			orig = &oid_orig;
-			if (!reflog_orig_head) {
-				strbuf_addstr(&msg, "updating ORIG_HEAD");
-				reflog_orig_head = msg.buf;
-			}
-			update_ref(reflog_orig_head, "ORIG_HEAD", orig,
-				   old_orig, 0, UPDATE_REFS_MSG_ON_ERR);
-		} else if (old_orig)
-			delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
-	}
-
-	if (!reflog_head) {
-		strbuf_setlen(&msg, prefix_len);
-		strbuf_addstr(&msg, "updating HEAD");
-		reflog_head = msg.buf;
-	}
-	if (!switch_to_branch)
-		ret = update_ref(reflog_head, "HEAD", oid, orig,
-				 detach_head ? REF_NO_DEREF : 0,
-				 UPDATE_REFS_MSG_ON_ERR);
-	else {
-		ret = update_ref(reflog_head, switch_to_branch, oid,
-				 NULL, 0, UPDATE_REFS_MSG_ON_ERR);
-		if (!ret)
-			ret = create_symref("HEAD", switch_to_branch,
-					    reflog_head);
-	}
-	if (run_hook)
-		run_hooks_l("post-checkout",
-			    oid_to_hex(orig ? orig : null_oid()),
-			    oid_to_hex(oid), "1", NULL);
+	if (oid != &head_oid || update_orig_head || switch_to_branch)
+		ret = update_refs(opts, oid, head);
 
 leave_reset_head:
-	strbuf_release(&msg);
 	rollback_lock_file(&lock);
 	clear_unpack_trees_porcelain(&unpack_tree_opts);
 	while (nr)
diff --git a/reset.h b/reset.h
index 12f83c78e2..a28f81829d 100644
--- a/reset.h
+++ b/reset.h
@@ -6,15 +6,55 @@
 
 #define GIT_REFLOG_ACTION_ENVIRONMENT "GIT_REFLOG_ACTION"
 
+/* Request a detached checkout */
 #define RESET_HEAD_DETACH (1<<0)
+/* Request a reset rather than a checkout */
 #define RESET_HEAD_HARD (1<<1)
+/* Run the post-checkout hook */
 #define RESET_HEAD_RUN_POST_CHECKOUT_HOOK (1<<2)
+/* Only update refs, do not touch the worktree */
 #define RESET_HEAD_REFS_ONLY (1<<3)
+/* Update ORIG_HEAD as well as HEAD */
 #define RESET_ORIG_HEAD (1<<4)
 
-int reset_head(struct repository *r, struct object_id *oid, const char *action,
-	       const char *switch_to_branch, unsigned flags,
-	       const char *reflog_orig_head, const char *reflog_head,
-	       const char *default_reflog_action);
+struct reset_head_opts {
+	/*
+	 * The commit to checkout/reset to. Defaults to HEAD.
+	 */
+	const struct object_id *oid;
+	/*
+	 * Optional value to set ORIG_HEAD. Defaults to HEAD.
+	 */
+	const struct object_id *orig_head;
+	/*
+	 * Optional branch to switch to.
+	 */
+	const char *branch;
+	/*
+	 * Flags defined above.
+	 */
+	unsigned flags;
+	/*
+	 * Optional reflog message for branch, defaults to head_msg.
+	 */
+	const char *branch_msg;
+	/*
+	 * Optional reflog message for HEAD, if this omitted but oid or branch
+	 * are given then default_reflog_action must be given.
+	 */
+	const char *head_msg;
+	/*
+	 * Optional reflog message for ORIG_HEAD, if this omitted and flags
+	 * contains RESET_ORIG_HEAD then default_reflog_action must be given.
+	 */
+	const char *orig_head_msg;
+	/*
+	 * Action to use in default reflog messages, only required if a ref is
+	 * being updated and the reflog messages above are omitted.
+	 */
+	const char *default_reflog_action;
+};
+
+int reset_head(struct repository *r, const struct reset_head_opts *opts);
 
 #endif
diff --git a/sequencer.c b/sequencer.c
index fb978a53a0..d3d73d86ad 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -4085,8 +4085,7 @@ static enum todo_command peek_command(struct todo_list *todo_list, int offset)
 	return -1;
 }
 
-void create_autostash(struct repository *r, const char *path,
-		      const char *default_reflog_action)
+void create_autostash(struct repository *r, const char *path)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct lock_file lock_file = LOCK_INIT;
@@ -4101,6 +4100,7 @@ void create_autostash(struct repository *r, const char *path,
 	if (has_unstaged_changes(r, 1) ||
 	    has_uncommitted_changes(r, 1)) {
 		struct child_process stash = CHILD_PROCESS_INIT;
+		struct reset_head_opts ropts = { .flags = RESET_HEAD_HARD };
 		struct object_id oid;
 
 		strvec_pushl(&stash.args,
@@ -4122,11 +4122,8 @@ void create_autostash(struct repository *r, const char *path,
 			    path);
 		write_file(path, "%s", oid_to_hex(&oid));
 		printf(_("Created autostash: %s\n"), buf.buf);
-		if (reset_head(r, NULL, "reset --hard",
-			       NULL, RESET_HEAD_HARD, NULL, NULL,
-			       default_reflog_action) < 0)
+		if (reset_head(r, &ropts) < 0)
 			die(_("could not reset --hard"));
-
 		if (discard_index(r->index) < 0 ||
 			repo_read_index(r) < 0)
 			die(_("could not read index"));
@@ -4211,47 +4208,26 @@ int apply_autostash_oid(const char *stash_oid)
 	return apply_save_autostash_oid(stash_oid, 1);
 }
 
-static int run_git_checkout(struct repository *r, struct replay_opts *opts,
-			    const char *commit, const char *action)
-{
-	struct child_process cmd = CHILD_PROCESS_INIT;
-	int ret;
-
-	cmd.git_cmd = 1;
-
-	if (startup_info->original_cwd) {
-		cmd.dir = startup_info->original_cwd;
-		strvec_pushf(&cmd.env_array, "%s=%s",
-			     GIT_WORK_TREE_ENVIRONMENT, r->worktree);
-	}
-	strvec_push(&cmd.args, "checkout");
-	strvec_push(&cmd.args, commit);
-	strvec_pushf(&cmd.env_array, GIT_REFLOG_ACTION "=%s", action);
-
-	if (opts->verbose)
-		ret = run_command(&cmd);
-	else
-		ret = run_command_silent_on_success(&cmd);
-
-	if (!ret)
-		discard_index(r->index);
-
-	return ret;
-}
-
 static int checkout_onto(struct repository *r, struct replay_opts *opts,
 			 const char *onto_name, const struct object_id *onto,
 			 const struct object_id *orig_head)
 {
-	const char *action = reflog_message(opts, "start", "checkout %s", onto_name);
-
-	if (run_git_checkout(r, opts, oid_to_hex(onto), action)) {
+	struct reset_head_opts ropts = {
+		.oid = onto,
+		.orig_head = orig_head,
+		.flags = RESET_HEAD_DETACH | RESET_ORIG_HEAD |
+				RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
+		.head_msg = reflog_message(opts, "start", "checkout %s",
+					   onto_name),
+		.default_reflog_action = "rebase"
+	};
+	if (reset_head(r, &ropts)) {
 		apply_autostash(rebase_path_autostash());
 		sequencer_remove_state(opts);
 		return error(_("could not detach HEAD"));
 	}
 
-	return update_ref(NULL, "ORIG_HEAD", orig_head, NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+	return 0;
 }
 
 static int stopped_at_head(struct repository *r)
diff --git a/sequencer.h b/sequencer.h
index 05a7d2ba6b..da64473636 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -197,8 +197,7 @@ void commit_post_rewrite(struct repository *r,
 			 const struct commit *current_head,
 			 const struct object_id *new_head);
 
-void create_autostash(struct repository *r, const char *path,
-		      const char *default_reflog_action);
+void create_autostash(struct repository *r, const char *path);
 int save_autostash(const char *path);
 int apply_autostash(const char *path);
 int apply_autostash_oid(const char *stash_oid);
diff --git a/t/t3406-rebase-message.sh b/t/t3406-rebase-message.sh
index 77a313f62e..d17b450e81 100755
--- a/t/t3406-rebase-message.sh
+++ b/t/t3406-rebase-message.sh
@@ -105,6 +105,29 @@ test_expect_success 'GIT_REFLOG_ACTION' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rebase --apply reflog' '
+	git checkout -b reflog-apply start &&
+	old_head_reflog="$(git log -g --format=%gs -1 HEAD)" &&
+
+	git rebase --apply Y &&
+
+	git log -g --format=%gs -4 HEAD >actual &&
+	cat >expect <<-EOF &&
+	rebase finished: returning to refs/heads/reflog-apply
+	rebase: Z
+	rebase: checkout Y
+	$old_head_reflog
+	EOF
+	test_cmp expect actual &&
+
+	git log -g --format=%gs -2 reflog-apply >actual &&
+	cat >expect <<-EOF &&
+	rebase finished: refs/heads/reflog-apply onto $(git rev-parse Y)
+	branch: Created from start
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success 'rebase -i onto unrelated history' '
 	git init unrelated &&
 	test_commit -C unrelated 1 &&
diff --git a/t/t3418-rebase-continue.sh b/t/t3418-rebase-continue.sh
index 22eca73aa3..130e2f9b55 100755
--- a/t/t3418-rebase-continue.sh
+++ b/t/t3418-rebase-continue.sh
@@ -308,4 +308,30 @@ test_expect_success 'there is no --no-reschedule-failed-exec in an ongoing rebas
 	test_expect_code 129 git rebase --edit-todo --no-reschedule-failed-exec
 '
 
+test_orig_head_helper () {
+	test_when_finished 'git rebase --abort &&
+		git checkout topic &&
+		git reset --hard commit-new-file-F2-on-topic-branch' &&
+	git update-ref -d ORIG_HEAD &&
+	test_must_fail git rebase "$@" &&
+	test_cmp_rev ORIG_HEAD commit-new-file-F2-on-topic-branch
+}
+
+test_orig_head () {
+	type=$1
+	test_expect_success "rebase $type sets ORIG_HEAD correctly" '
+		git checkout topic &&
+		git reset --hard commit-new-file-F2-on-topic-branch &&
+		test_orig_head_helper $type main
+	'
+
+	test_expect_success "rebase $type <upstream> <branch> sets ORIG_HEAD correctly" '
+		git checkout main &&
+		test_orig_head_helper $type main topic
+	'
+}
+
+test_orig_head --apply
+test_orig_head --merge
+
 test_done
diff --git a/t/t5403-post-checkout-hook.sh b/t/t5403-post-checkout-hook.sh
index 1ec9e23be7..d118181690 100755
--- a/t/t5403-post-checkout-hook.sh
+++ b/t/t5403-post-checkout-hook.sh
@@ -49,23 +49,60 @@ test_expect_success 'post-checkout receives the right args when not switching br
 	test $old = $new && test $flag = 0
 '
 
-test_expect_success 'post-checkout is triggered on rebase' '
-	test_when_finished "rm -f .git/post-checkout.args" &&
-	git checkout -b rebase-test main &&
-	rm -f .git/post-checkout.args &&
-	git rebase rebase-on-me &&
-	read old new flag <.git/post-checkout.args &&
-	test $old != $new && test $flag = 1
-'
+test_rebase () {
+	args="$*" &&
+	test_expect_success "post-checkout is triggered on rebase $args" '
+		test_when_finished "rm -f .git/post-checkout.args" &&
+		git checkout -B rebase-test main &&
+		rm -f .git/post-checkout.args &&
+		git rebase $args rebase-on-me &&
+		read old new flag <.git/post-checkout.args &&
+		test_cmp_rev main $old &&
+		test_cmp_rev rebase-on-me $new &&
+		test $flag = 1
+	'
+
+	test_expect_success "post-checkout is triggered on rebase $args with fast-forward" '
+		test_when_finished "rm -f .git/post-checkout.args" &&
+		git checkout -B ff-rebase-test rebase-on-me^ &&
+		rm -f .git/post-checkout.args &&
+		git rebase $args rebase-on-me &&
+		read old new flag <.git/post-checkout.args &&
+		test_cmp_rev rebase-on-me^ $old &&
+		test_cmp_rev rebase-on-me $new &&
+		test $flag = 1
+	'
+
+	test_expect_success "rebase $args fast-forward branch checkout runs post-checkout hook" '
+		test_when_finished "test_might_fail git rebase --abort" &&
+		test_when_finished "rm -f .git/post-checkout.args" &&
+		git update-ref refs/heads/rebase-fast-forward three &&
+		git checkout two  &&
+		rm -f .git/post-checkout.args &&
+		git rebase $args HEAD rebase-fast-forward  &&
+		read old new flag <.git/post-checkout.args &&
+		test_cmp_rev two $old &&
+		test_cmp_rev three $new &&
+		test $flag = 1
+	'
+
+	test_expect_success "rebase $args checkout does not remove untracked files" '
+		test_when_finished "test_might_fail git rebase --abort" &&
+		test_when_finished "rm -f .git/post-checkout.args" &&
+		git update-ref refs/heads/rebase-fast-forward three &&
+		git checkout two &&
+		rm -f .git/post-checkout.args &&
+		echo untracked >three.t &&
+		test_when_finished "rm three.t" &&
+		test_must_fail git rebase $args HEAD rebase-fast-forward 2>err &&
+		grep "untracked working tree files would be overwritten by checkout" err &&
+		test_path_is_missing .git/post-checkout.args
 
-test_expect_success 'post-checkout is triggered on rebase with fast-forward' '
-	test_when_finished "rm -f .git/post-checkout.args" &&
-	git checkout -b ff-rebase-test rebase-on-me^ &&
-	rm -f .git/post-checkout.args &&
-	git rebase rebase-on-me &&
-	read old new flag <.git/post-checkout.args &&
-	test $old != $new && test $flag = 1
 '
+}
+
+test_rebase --apply &&
+test_rebase --merge
 
 test_expect_success 'post-checkout hook is triggered by clone' '
 	mkdir -p templates/hooks &&