[PATCH v2 2/4] am: support --always option to am empty commits

["Aleen via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Aleen <aleen42@xxxxxxxxxx>

Signed-off-by: Aleen <aleen42@xxxxxxxxxx>
---
 Documentation/git-am.txt |  5 +++++
 builtin/am.c             | 18 ++++++++++++++++--
 t/t4150-am.sh            | 25 +++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..de5d11e404c 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>]
+	 [--always]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 
@@ -159,6 +160,10 @@ default.   You can use `--no-utf8` to override this.
 	countermand both `commit.gpgSign` configuration variable, and
 	earlier `--gpg-sign`.
 
+--always::
+	Apply patches of commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-format-patch[1])
+
 --continue::
 -r::
 --resolved::
diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..d11efc16f92 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -124,6 +124,8 @@ struct am_state {
 	int ignore_date;
 	int allow_rerere_autoupdate;
 	const char *sign_commit;
+	int always;
+	int empty_commit;
 	int rebasing;
 };
 
@@ -1249,8 +1251,12 @@ static int parse_mail(struct am_state *state, const char *mail)
 	}
 
 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
+		if (state->always) {
+			state->empty_commit = 1;
+		} else {
+			printf_ln(_("Patch is empty."));
+			die_user_resolve(state);
+		}
 	}
 
 	strbuf_addstr(&msg, "\n\n");
@@ -1792,6 +1798,9 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (state->empty_commit)
+			goto commit;
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 
@@ -1827,6 +1836,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:
@@ -2357,6 +2367,10 @@ 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_BOOL(0, "always", &state.always,
+			N_("always apply patch event if the patch is empty")),
+		OPT_HIDDEN_BOOL(0, "empty-commit", &state.empty_commit,
+			N_("(internal use for skipping git-apply to empty commits)")),
 		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..5b3617857a8 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 &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick
@@ -1152,4 +1158,23 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'am a real empty patch with the --always option' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	test_must_fail git am --always empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'am a patch with empty commits' '
+	grep "empty commit" empty-commit.patch &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	git checkout empty-commit^ &&
+	git am --always empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git cat-file commit HEAD >actual &&
+	test_i18ngrep "empty commit" actual
+'
+
 test_done
-- 
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