Merge branch 'ra/cherry-pick-revert-skip'

"git cherry-pick/revert" learned a new "--skip" action.

* ra/cherry-pick-revert-skip:
  cherry-pick/revert: advise using --skip
  cherry-pick/revert: add --skip option
  sequencer: use argv_array in reset_merge
  sequencer: rename reset_for_rollback to reset_merge
  sequencer: add advice for revert

sequencer.c

@@ -2654,15 +2654,41 @@ static int walk_revs_populate_todo(struct todo_list *todo_list,
 	return 0;
 }
 
-static int create_seq_dir(void)
+static int create_seq_dir(struct repository *r)
 {
-	if (file_exists(git_path_seq_dir())) {
-		error(_("a cherry-pick or revert is already in progress"));
-		advise(_("try \"git cherry-pick (--continue | --quit | --abort)\""));
+	enum replay_action action;
+	const char *in_progress_error = NULL;
+	const char *in_progress_advice = NULL;
+	unsigned int advise_skip = file_exists(git_path_revert_head(r)) ||
+				file_exists(git_path_cherry_pick_head(r));
+
+	if (!sequencer_get_last_command(r, &action)) {
+		switch (action) {
+		case REPLAY_REVERT:
+			in_progress_error = _("revert is already in progress");
+			in_progress_advice =
+			_("try \"git revert (--continue | %s--abort | --quit)\"");
+			break;
+		case REPLAY_PICK:
+			in_progress_error = _("cherry-pick is already in progress");
+			in_progress_advice =
+			_("try \"git cherry-pick (--continue | %s--abort | --quit)\"");
+			break;
+		default:
+			BUG("unexpected action in create_seq_dir");
+		}
+	}
+	if (in_progress_error) {
+		error("%s", in_progress_error);
+		if (advice_sequencer_in_use)
+			advise(in_progress_advice,
+				advise_skip ? "--skip | " : "");
 		return -1;
-	} else if (mkdir(git_path_seq_dir(), 0777) < 0)
+	}
+	if (mkdir(git_path_seq_dir(), 0777) < 0)
 		return error_errno(_("could not create sequencer directory '%s'"),
 				   git_path_seq_dir());
+
 	return 0;
 }
 
@@ -2713,15 +2739,20 @@ static int rollback_is_safe(void)
 	return oideq(&actual_head, &expected_head);
 }
 
-static int reset_for_rollback(const struct object_id *oid)
+static int reset_merge(const struct object_id *oid)
 {
-	const char *argv[4];	/* reset --merge <arg> + NULL */
+	int ret;
+	struct argv_array argv = ARGV_ARRAY_INIT;
 
-	argv[0] = "reset";
-	argv[1] = "--merge";
-	argv[2] = oid_to_hex(oid);
-	argv[3] = NULL;
-	return run_command_v_opt(argv, RUN_GIT_CMD);
+	argv_array_pushl(&argv, "reset", "--merge", NULL);
+
+	if (!is_null_oid(oid))
+		argv_array_push(&argv, oid_to_hex(oid));
+
+	ret = run_command_v_opt(argv.argv, RUN_GIT_CMD);
+	argv_array_clear(&argv);
+
+	return ret;
 }
 
 static int rollback_single_pick(struct repository *r)
@@ -2735,7 +2766,16 @@ static int rollback_single_pick(struct repository *r)
 		return error(_("cannot resolve HEAD"));
 	if (is_null_oid(&head_oid))
 		return error(_("cannot abort from a branch yet to be born"));
-	return reset_for_rollback(&head_oid);
+	return reset_merge(&head_oid);
+}
+
+static int skip_single_pick(void)
+{
+	struct object_id head;
+
+	if (read_ref_full("HEAD", 0, &head, NULL))
+		return error(_("cannot resolve HEAD"));
+	return reset_merge(&head);
 }
 
 int sequencer_rollback(struct repository *r, struct replay_opts *opts)
@@ -2778,7 +2818,7 @@ int sequencer_rollback(struct repository *r, struct replay_opts *opts)
 		warning(_("You seem to have moved HEAD. "
 			  "Not rewinding, check your HEAD!"));
 	} else
-	if (reset_for_rollback(&oid))
+	if (reset_merge(&oid))
 		goto fail;
 	strbuf_release(&buf);
 	return sequencer_remove_state(opts);
@@ -2787,6 +2827,70 @@ fail:
 	return -1;
 }
 
+int sequencer_skip(struct repository *r, struct replay_opts *opts)
+{
+	enum replay_action action = -1;
+	sequencer_get_last_command(r, &action);
+
+	/*
+	 * Check whether the subcommand requested to skip the commit is actually
+	 * in progress and that it's safe to skip the commit.
+	 *
+	 * opts->action tells us which subcommand requested to skip the commit.
+	 * If the corresponding .git/<ACTION>_HEAD exists, we know that the
+	 * action is in progress and we can skip the commit.
+	 *
+	 * Otherwise we check that the last instruction was related to the
+	 * particular subcommand we're trying to execute and barf if that's not
+	 * the case.
+	 *
+	 * Finally we check that the rollback is "safe", i.e., has the HEAD
+	 * moved? In this case, it doesn't make sense to "reset the merge" and
+	 * "skip the commit" as the user already handled this by committing. But
+	 * we'd not want to barf here, instead give advice on how to proceed. We
+	 * only need to check that when .git/<ACTION>_HEAD doesn't exist because
+	 * it gets removed when the user commits, so if it still exists we're
+	 * sure the user can't have committed before.
+	 */
+	switch (opts->action) {
+	case REPLAY_REVERT:
+		if (!file_exists(git_path_revert_head(r))) {
+			if (action != REPLAY_REVERT)
+				return error(_("no revert in progress"));
+			if (!rollback_is_safe())
+				goto give_advice;
+		}
+		break;
+	case REPLAY_PICK:
+		if (!file_exists(git_path_cherry_pick_head(r))) {
+			if (action != REPLAY_PICK)
+				return error(_("no cherry-pick in progress"));
+			if (!rollback_is_safe())
+				goto give_advice;
+		}
+		break;
+	default:
+		BUG("unexpected action in sequencer_skip");
+	}
+
+	if (skip_single_pick())
+		return error(_("failed to skip the commit"));
+	if (!is_directory(git_path_seq_dir()))
+		return 0;
+
+	return sequencer_continue(r, opts);
+
+give_advice:
+	error(_("there is nothing to skip"));
+
+	if (advice_resolve_conflict) {
+		advise(_("have you committed already?\n"
+			 "try \"git %s --continue\""),
+			 action == REPLAY_REVERT ? "revert" : "cherry-pick");
+	}
+	return -1;
+}
+
 static int save_todo(struct todo_list *todo_list, struct replay_opts *opts)
 {
 	struct lock_file todo_lock = LOCK_INIT;
@@ -4257,7 +4361,7 @@ int sequencer_pick_revisions(struct repository *r,
 	 */
 
 	if (walk_revs_populate_todo(&todo_list, opts) ||
-			create_seq_dir() < 0)
+			create_seq_dir(r) < 0)
 		return -1;
 	if (get_oid("HEAD", &oid) && (opts->action == REPLAY_REVERT))
 		return error(_("can't revert as initial commit"));