Merge branch 'bl/cherry-pick-empty'

Allow git-cherry-pick(1) to automatically drop redundant commits via
a new `--empty` option, similar to the `--empty` options for
git-rebase(1) and git-am(1). Includes a soft deprecation of
`--keep-redundant-commits` as well as some related docs changes and
sequencer code cleanup.

* bl/cherry-pick-empty:
  cherry-pick: add `--empty` for more robust redundant commit handling
  cherry-pick: enforce `--keep-redundant-commits` incompatibility
  sequencer: do not require `allow_empty` for redundant commit options
  sequencer: handle unborn branch with `--allow-empty`
  rebase: update `--empty=ask` to `--empty=stop`
  docs: clean up `--empty` formatting in git-rebase(1) and git-am(1)
  docs: address inaccurate `--empty` default with `--exec`

Author: gitster

Documentation/git-am.txt

@@ -66,13 +66,19 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
---empty=(stop|drop|keep)::
-	By default, or when the option is set to 'stop', the command
-	errors out on an input e-mail message lacking a patch
-	and stops in the middle of the current am session. When this
-	option is set to 'drop', skip such an e-mail message instead.
-	When this option is set to 'keep', create an empty commit,
-	recording the contents of the e-mail message as its log.
+--empty=(drop|keep|stop)::
+	How to handle an e-mail message lacking a patch:
++
+--
+`drop`;;
+	The e-mail message will be skipped.
+`keep`;;
+	An empty commit will be created, with the contents of the e-mail
+	message as its log.
+`stop`;;
+	The command will fail, stopping in the middle of the current `am`
+	session. This is the default behavior.
+--
 
 -m::
 --message-id::

Documentation/git-cherry-pick.txt

@@ -131,20 +131,36 @@ effect to your index in a row.
 	even without this option.  Note also, that use of this option only
 	keeps commits that were initially empty (i.e. the commit recorded the
 	same tree as its parent).  Commits which are made empty due to a
-	previous commit are dropped.  To force the inclusion of those commits
-	use `--keep-redundant-commits`.
+	previous commit will cause the cherry-pick to fail.  To force the
+	inclusion of those commits, use `--empty=keep`.
 
 --allow-empty-message::
 	By default, cherry-picking a commit with an empty message will fail.
 	This option overrides that behavior, allowing commits with empty
 	messages to be cherry picked.
 
+--empty=(drop|keep|stop)::
+	How to handle commits being cherry-picked that are redundant with
+	changes already in the current history.
++
+--
+`drop`;;
+	The commit will be dropped.
+`keep`;;
+	The commit will be kept. Implies `--allow-empty`.
+`stop`;;
+	The cherry-pick will stop when the commit is applied, allowing
+	you to examine the commit. This is the default behavior.
+--
++
+Note that `--empty=drop` and `--empty=stop` only specify how to handle a
+commit that was not initially empty, but rather became empty due to a previous
+commit. Commits that were initially empty will still cause the cherry-pick to
+fail unless one of `--empty=keep` or `--allow-empty` are specified.
++
+
 --keep-redundant-commits::
-	If a commit being cherry picked duplicates a commit already in the
-	current history, it will become empty.  By default these
-	redundant commits cause `cherry-pick` to stop so the user can
-	examine the commit. This option overrides that behavior and
-	creates an empty commit object.  Implies `--allow-empty`.
+	Deprecated synonym for `--empty=keep`.
 
 --strategy=<strategy>::
 	Use the given merge strategy.  Should only be used once.

Documentation/git-rebase.txt

@@ -289,17 +289,25 @@ See also INCOMPATIBLE OPTIONS below.
 +
 See also INCOMPATIBLE OPTIONS below.
 
---empty=(drop|keep|ask)::
+--empty=(drop|keep|stop)::
 	How to handle commits that are not empty to start and are not
 	clean cherry-picks of any upstream commit, but which become
 	empty after rebasing (because they contain a subset of already
-	upstream changes).  With drop (the default), commits that
-	become empty are dropped.  With keep, such commits are kept.
-	With ask (implied by `--interactive`), the rebase will halt when
-	an empty commit is applied allowing you to choose whether to
-	drop it, edit files more, or just commit the empty changes.
-	Other options, like `--exec`, will use the default of drop unless
-	`-i`/`--interactive` is explicitly specified.
+	upstream changes):
++
+--
+`drop`;;
+	The commit will be dropped. This is the default behavior.
+`keep`;;
+	The commit will be kept. This option is implied when `--exec` is
+	specified unless `-i`/`--interactive` is also specified.
+`stop`;;
+`ask`;;
+	The rebase will halt when the commit is applied, allowing you to
+	choose whether to drop it, edit files more, or just commit the empty
+	changes. This option is implied when `-i`/`--interactive` is
+	specified. `ask` is a deprecated synonym of `stop`.
+--
 +
 Note that commits which start empty are kept (unless `--no-keep-empty`
 is specified), and commits which are clean cherry-picks (as determined
@@ -704,7 +712,7 @@ be dropped automatically with `--no-keep-empty`).
 Similar to the apply backend, by default the merge backend drops
 commits that become empty unless `-i`/`--interactive` is specified (in
 which case it stops and asks the user what to do).  The merge backend
-also has an `--empty=(drop|keep|ask)` option for changing the behavior
+also has an `--empty=(drop|keep|stop)` option for changing the behavior
 of handling commits that become empty.
 
 Directory rename detection

builtin/rebase.c

@@ -58,7 +58,7 @@ enum empty_type {
 	EMPTY_UNSPECIFIED = -1,
 	EMPTY_DROP,
 	EMPTY_KEEP,
-	EMPTY_ASK
+	EMPTY_STOP
 };
 
 enum action {
@@ -945,10 +945,14 @@ static enum empty_type parse_empty_value(const char *value)
 		return EMPTY_DROP;
 	else if (!strcasecmp(value, "keep"))
 		return EMPTY_KEEP;
-	else if (!strcasecmp(value, "ask"))
-		return EMPTY_ASK;
+	else if (!strcasecmp(value, "stop"))
+		return EMPTY_STOP;
+	else if (!strcasecmp(value, "ask")) {
+		warning(_("--empty=ask is deprecated; use '--empty=stop' instead."));
+		return EMPTY_STOP;
+	}
 
-	die(_("unrecognized empty type '%s'; valid values are \"drop\", \"keep\", and \"ask\"."), value);
+	die(_("unrecognized empty type '%s'; valid values are \"drop\", \"keep\", and \"stop\"."), value);
 }
 
 static int parse_opt_keep_empty(const struct option *opt, const char *arg,
@@ -1127,7 +1131,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 				 "instead of ignoring them"),
 			      1, PARSE_OPT_HIDDEN),
 		OPT_RERERE_AUTOUPDATE(&options.allow_rerere_autoupdate),
-		OPT_CALLBACK_F(0, "empty", &options, "(drop|keep|ask)",
+		OPT_CALLBACK_F(0, "empty", &options, "(drop|keep|stop)",
 			       N_("how to handle commits that become empty"),
 			       PARSE_OPT_NONEG, parse_opt_empty),
 		OPT_CALLBACK_F('k', "keep-empty", &options, NULL,
@@ -1544,7 +1548,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	if (options.empty == EMPTY_UNSPECIFIED) {
 		if (options.flags & REBASE_INTERACTIVE_EXPLICIT)
-			options.empty = EMPTY_ASK;
+			options.empty = EMPTY_STOP;
 		else if (options.exec.nr > 0)
 			options.empty = EMPTY_KEEP;
 		else

builtin/revert.c

@@ -43,6 +43,31 @@ static const char * const *revert_or_cherry_pick_usage(struct replay_opts *opts)
 	return opts->action == REPLAY_REVERT ? revert_usage : cherry_pick_usage;
 }
 
+enum empty_action {
+	EMPTY_COMMIT_UNSPECIFIED = -1,
+	STOP_ON_EMPTY_COMMIT,      /* output errors and stop in the middle of a cherry-pick */
+	DROP_EMPTY_COMMIT,         /* skip with a notice message */
+	KEEP_EMPTY_COMMIT,         /* keep recording as empty commits */
+};
+
+static int parse_opt_empty(const struct option *opt, const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
+	if (!strcmp(arg, "stop"))
+		*opt_value = STOP_ON_EMPTY_COMMIT;
+	else if (!strcmp(arg, "drop"))
+		*opt_value = DROP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "keep"))
+		*opt_value = KEEP_EMPTY_COMMIT;
+	else
+		return error(_("invalid value for '%s': '%s'"), "--empty", arg);
+
+	return 0;
+}
+
 static int option_parse_m(const struct option *opt,
 			  const char *arg, int unset)
 {
@@ -85,6 +110,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 	const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 	const char *me = action_name(opts);
 	const char *cleanup_arg = NULL;
+	enum empty_action empty_opt = EMPTY_COMMIT_UNSPECIFIED;
 	int cmd = 0;
 	struct option base_options[] = {
 		OPT_CMDMODE(0, "quit", &cmd, N_("end revert or cherry-pick sequence"), 'q'),
@@ -114,7 +140,10 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 			OPT_BOOL(0, "ff", &opts->allow_ff, N_("allow fast-forward")),
 			OPT_BOOL(0, "allow-empty", &opts->allow_empty, N_("preserve initially empty commits")),
 			OPT_BOOL(0, "allow-empty-message", &opts->allow_empty_message, N_("allow commits with empty messages")),
-			OPT_BOOL(0, "keep-redundant-commits", &opts->keep_redundant_commits, N_("keep redundant, empty commits")),
+			OPT_BOOL(0, "keep-redundant-commits", &opts->keep_redundant_commits, N_("deprecated: use --empty=keep instead")),
+			OPT_CALLBACK_F(0, "empty", &empty_opt, "(stop|drop|keep)",
+				       N_("how to handle commits that become empty"),
+				       PARSE_OPT_NONEG, parse_opt_empty),
 			OPT_END(),
 		};
 		options = parse_options_concat(options, cp_extra);
@@ -134,6 +163,11 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 
+	if (opts->action == REPLAY_PICK) {
+		opts->drop_redundant_commits = (empty_opt == DROP_EMPTY_COMMIT);
+		opts->keep_redundant_commits = opts->keep_redundant_commits || (empty_opt == KEEP_EMPTY_COMMIT);
+	}
+
 	/* implies allow_empty */
 	if (opts->keep_redundant_commits)
 		opts->allow_empty = 1;
@@ -167,6 +201,8 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 				"--ff", opts->allow_ff,
 				"--rerere-autoupdate", opts->allow_rerere_auto == RERERE_AUTOUPDATE,
 				"--no-rerere-autoupdate", opts->allow_rerere_auto == RERERE_NOAUTOUPDATE,
+				"--keep-redundant-commits", opts->keep_redundant_commits,
+				"--empty", empty_opt != EMPTY_COMMIT_UNSPECIFIED,
 				NULL);
 	}
 

sequencer.c

@@ -787,29 +787,42 @@ static struct object_id *get_cache_tree_oid(struct index_state *istate)
 static int is_index_unchanged(struct repository *r)
 {
 	struct object_id head_oid, *cache_tree_oid;
+	const struct object_id *head_tree_oid;
 	struct commit *head_commit;
 	struct index_state *istate = r->index;
+	const char *head_name;
+
+	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL)) {
+		/* Check to see if this is an unborn branch */
+		head_name = resolve_ref_unsafe("HEAD",
+			RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
+			&head_oid, NULL);
+		if (!head_name ||
+			!starts_with(head_name, "refs/heads/") ||
+			!is_null_oid(&head_oid))
+			return error(_("could not resolve HEAD commit"));
+		head_tree_oid = the_hash_algo->empty_tree;
+	} else {
+		head_commit = lookup_commit(r, &head_oid);
 
-	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
-		return error(_("could not resolve HEAD commit"));
-
-	head_commit = lookup_commit(r, &head_oid);
+		/*
+		 * If head_commit is NULL, check_commit, called from
+		 * lookup_commit, would have indicated that head_commit is not
+		 * a commit object already.  repo_parse_commit() will return failure
+		 * without further complaints in such a case.  Otherwise, if
+		 * the commit is invalid, repo_parse_commit() will complain.  So
+		 * there is nothing for us to say here.  Just return failure.
+		 */
+		if (repo_parse_commit(r, head_commit))
+			return -1;
 
-	/*
-	 * If head_commit is NULL, check_commit, called from
-	 * lookup_commit, would have indicated that head_commit is not
-	 * a commit object already.  repo_parse_commit() will return failure
-	 * without further complaints in such a case.  Otherwise, if
-	 * the commit is invalid, repo_parse_commit() will complain.  So
-	 * there is nothing for us to say here.  Just return failure.
-	 */
-	if (repo_parse_commit(r, head_commit))
-		return -1;
+		head_tree_oid = get_commit_tree_oid(head_commit);
+	}
 
 	if (!(cache_tree_oid = get_cache_tree_oid(istate)))
 		return -1;
 
-	return oideq(cache_tree_oid, get_commit_tree_oid(head_commit));
+	return oideq(cache_tree_oid, head_tree_oid);
 }
 
 static int write_author_script(const char *message)
@@ -1736,34 +1749,25 @@ static int allow_empty(struct repository *r,
 	int index_unchanged, originally_empty;
 
 	/*
-	 * Four cases:
-	 *
-	 * (1) we do not allow empty at all and error out.
+	 * For a commit that is initially empty, allow_empty determines if it
+	 * should be kept or not
 	 *
-	 * (2) we allow ones that were initially empty, and
-	 *     just drop the ones that become empty
-	 *
-	 * (3) we allow ones that were initially empty, but
-	 *     halt for the ones that become empty;
-	 *
-	 * (4) we allow both.
+	 * For a commit that becomes empty, keep_redundant_commits and
+	 * drop_redundant_commits determine whether the commit should be kept or
+	 * dropped. If neither is specified, halt.
 	 */
-	if (!opts->allow_empty)
-		return 0; /* let "git commit" barf as necessary */
-
 	index_unchanged = is_index_unchanged(r);
 	if (index_unchanged < 0)
 		return index_unchanged;
 	if (!index_unchanged)
 		return 0; /* we do not have to say --allow-empty */
 
-	if (opts->keep_redundant_commits)
-		return 1;
-
 	originally_empty = is_original_commit_empty(commit);
 	if (originally_empty < 0)
 		return originally_empty;
 	if (originally_empty)
+		return opts->allow_empty;
+	else if (opts->keep_redundant_commits)
 		return 1;
 	else if (opts->drop_redundant_commits)
 		return 2;
@@ -2943,6 +2947,9 @@ static int populate_opts_cb(const char *key, const char *value,
 	else if (!strcmp(key, "options.allow-empty-message"))
 		opts->allow_empty_message =
 			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
+	else if (!strcmp(key, "options.drop-redundant-commits"))
+		opts->drop_redundant_commits =
+			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
 	else if (!strcmp(key, "options.keep-redundant-commits"))
 		opts->keep_redundant_commits =
 			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
@@ -3487,6 +3494,9 @@ static int save_opts(struct replay_opts *opts)
 	if (opts->allow_empty_message)
 		res |= git_config_set_in_file_gently(opts_file,
 				"options.allow-empty-message", "true");
+	if (opts->drop_redundant_commits)
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.drop-redundant-commits", "true");
 	if (opts->keep_redundant_commits)
 		res |= git_config_set_in_file_gently(opts_file,
 				"options.keep-redundant-commits", "true");