[v17,2/3] am: support --empty=<option> to handle empty patches

Commit Message

徐沛文 (Aleen) Dec. 7, 2021, 8:31 a.m. UTC

From: =?UTF-8?q?=E5=BE=90=E6=B2=9B=E6=96=87=20=28Aleen=29?=
 <[e-mail]>

Since that the command 'git-format-patch' can include patches of
commits that emit no changes, the 'git-am' command should also
support an option, named as '--empty', to specify how to handle
those empty patches. In this commit, we have implemented three
valid options ('stop', 'drop' and 'keep').

Signed-off-by: 徐沛文 (Aleen) <[e-mail]>
---
 Documentation/git-am.txt |  9 +++++++
 builtin/am.c             | 55 ++++++++++++++++++++++++++++++++++++----
 t/t4150-am.sh            | 49 +++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 5 deletions(-)

Comments

Junio C Hamano Dec. 7, 2021, 6:12 p.m. UTC | #1

""徐沛文 (Aleen)" via GitGitGadget"  <[e-mail]>
writes:


This step look mostly good and well done, except for just a few
things that remain.

> +enum empty_action {
> +	STOP_ON_EMPTY_COMMIT = 0,  /* output errors and stop in the middle of an am session */
> +	DROP_EMPTY_COMMIT,         /* skip with a notice message, unless "--quiet" has been passed */
> +	KEEP_EMPTY_COMMIT          /* keep recording as empty commits */
> +};

It is friendly to future developers to end the last item in enum
with a comma, unless the current last item MUST stay to be the last
one even when they add new ones.  I.e.

	KEEP_EMPTY_COMMIT,          /* keep recording as empty commits */

>  struct am_state {
>  	/* state directory path */
>  	char *dir;
> @@ -118,6 +124,7 @@ struct am_state {
>  	int message_id;
>  	int scissors; /* enum scissors_type */
>  	int quoted_cr; /* enum quoted_cr_action */
> +	int empty_type; /* enum empty_action */

Mental note.  After this series graduates to 'master', at some point
in the future, we should clean these members up to be of their
respective enum types, not "int".

> @@ -1763,6 +1784,7 @@ static void am_run(struct am_state *state, int resume)
>  	while (state->cur <= state->last) {
>  		const char *mail = am_path(state, msgnum(state));
>  		int apply_status;
> +		int to_keep;
>  
>  		reset_ident_date();
>  
> @@ -1792,8 +1814,27 @@ static void am_run(struct am_state *state, int resume)
>  		if (state->interactive && do_interactive(state))
>  			goto next;
>  
> +		to_keep = 0;
> +		if (is_empty_or_missing_file(am_path(state, "patch"))) {
> +			switch (state->empty_type) {
> +			case DROP_EMPTY_COMMIT:
> +				say(state, stdout, _("Skipping: %.*s"), linelen(state->msg), state->msg);
> +				goto next;
> +				break;
> +			case KEEP_EMPTY_COMMIT:
> +				to_keep = 1;

This causes the code that produces the "Applying" message jumped
over, so the user will not see anything done for this step.  

I think we want to mimic the above case arm and do something like

				say(state, stdout, _("Creating an empty commit: %.*s"),
					linelen(state->msg), state->msg);

to avoid being mum about what was done in this step.

> +				break;
> +			case STOP_ON_EMPTY_COMMIT:
> +				printf_ln(_("Patch is empty."));
> +				die_user_resolve(state);
> +				break;
> +			}
> +		}
> +
>  		if (run_applypatch_msg_hook(state))
>  			exit(1);
> +		if (to_keep)
> +			goto commit;
>  
>  		say(state, stdout, _("Applying: %.*s"), linelen(state->msg), state->msg);
>  
> @@ -1827,6 +1868,7 @@ static void am_run(struct am_state *state, int resume)
>  			die_user_resolve(state);
>  		}
>  
> +commit:
>  		do_commit(state);
>  
>  next:

> +test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
> +	git am --empty=keep empty-commit.patch &&
> +	test_path_is_missing .git/rebase-apply &&
> +	git show empty-commit --format="%s" >expected &&
> +	git show HEAD --format="%s" >actual &&

For the test data prepared by the earlier part of this patch, this
does not make a difference, but by using %B instead of %s, I think
you can catch a future bug that only keeps the subject intact while
munging the body of the message.

Other than these, looking quite good.

Thanks.

Patch

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..7676bd58ae7 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt
@@ -16,6 +16,7 @@  SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--empty=(stop|drop|keep)]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 
@@ -63,6 +64,14 @@  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 into 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.
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),
diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..f45aa33366f 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -87,6 +87,12 @@  enum show_patch_type {
 	SHOW_PATCH_DIFF = 1,
 };
 
+enum empty_action {
+	STOP_ON_EMPTY_COMMIT = 0,  /* output errors and stop in the middle of an am session */
+	DROP_EMPTY_COMMIT,         /* skip with a notice message, unless "--quiet" has been passed */
+	KEEP_EMPTY_COMMIT          /* keep recording as empty commits */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;
@@ -118,6 +124,7 @@  struct am_state {
 	int message_id;
 	int scissors; /* enum scissors_type */
 	int quoted_cr; /* enum quoted_cr_action */
+	int empty_type; /* enum empty_action */
 	struct strvec git_apply_opts;
 	const char *resolvemsg;
 	int committer_date_is_author_date;
@@ -178,6 +185,25 @@  static int am_option_parse_quoted_cr(const struct option *opt,
 	return 0;
 }
 
+static int am_option_parse_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 --empty: %s"), arg);
+
+	return 0;
+}
+
 /**
  * Returns path relative to the am_state directory.
  */
@@ -1248,11 +1274,6 @@  static int parse_mail(struct am_state *state, const char *mail)
 		goto finish;
 	}
 
-	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
-	}
-
 	strbuf_addstr(&msg, "\n\n");
 	strbuf_addbuf(&msg, &mi.log_message);
 	strbuf_stripspace(&msg, 0);
@@ -1763,6 +1784,7 @@  static void am_run(struct am_state *state, int resume)
 	while (state->cur <= state->last) {
 		const char *mail = am_path(state, msgnum(state));
 		int apply_status;
+		int to_keep;
 
 		reset_ident_date();
 
@@ -1792,8 +1814,27 @@  static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		to_keep = 0;
+		if (is_empty_or_missing_file(am_path(state, "patch"))) {
+			switch (state->empty_type) {
+			case DROP_EMPTY_COMMIT:
+				say(state, stdout, _("Skipping: %.*s"), linelen(state->msg), state->msg);
+				goto next;
+				break;
+			case KEEP_EMPTY_COMMIT:
+				to_keep = 1;
+				break;
+			case STOP_ON_EMPTY_COMMIT:
+				printf_ln(_("Patch is empty."));
+				die_user_resolve(state);
+				break;
+			}
+		}
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
+		if (to_keep)
+			goto commit;
 
 		say(state, stdout, _("Applying: %.*s"), linelen(state->msg), state->msg);
 
@@ -1827,6 +1868,7 @@  static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:
@@ -2357,6 +2399,9 @@  int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_CALLBACK_F(STOP_ON_EMPTY_COMMIT, "empty", &state.empty_type, "{stop,drop,keep}",
+		  N_("how to handle empty patches"),
+		  PARSE_OPT_NONEG, am_option_parse_empty),
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()
diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..ce8e8e79ace 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh
@@ -196,6 +196,12 @@  test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	: >empty.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick
@@ -1152,4 +1158,47 @@  test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'an empty input file is error regardless of --empty option' '
+	test_when_finished "git am --abort || :" &&
+	test_must_fail git am --empty=drop empty.patch 2>actual &&
+	echo "Patch format detection failed." >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'invalid when passing the --empty option alone' '
+	test_when_finished "git am --abort || :" &&
+	git checkout empty-commit^ &&
+	test_must_fail git am --empty empty-commit.patch 2>err &&
+	echo "error: Invalid value for --empty: empty-commit.patch" >expected &&
+	test_cmp expected err
+'
+
+test_expect_success 'a message without a patch is an error (default)' '
+	test_when_finished "git am --abort || :" &&
+	test_must_fail git am empty-commit.patch >err &&
+	grep "Patch is empty" err
+'
+
+test_expect_success 'a message without a patch is an error where an explicit "--empty=stop" is given' '
+	test_when_finished "git am --abort || :" &&
+	test_must_fail git am --empty=stop empty-commit.patch >err &&
+	grep "Patch is empty." err
+'
+
+test_expect_success 'a message without a patch will be skipped when "--empty=drop" is given' '
+	git am --empty=drop empty-commit.patch >output &&
+	git rev-parse empty-commit^ >expected &&
+	git rev-parse HEAD >actual &&
+	test_cmp expected actual &&
+	grep "Skipping: empty commit" output
+'
+
+test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
+	git am --empty=keep empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git show empty-commit --format="%s" >expected &&
+	git show HEAD --format="%s" >actual &&
+	test_cmp actual expected
+'
+
 test_done