am: let --signoff override --no-signoff

After resolving a conflicting patch, a user may wish to sign off the
patch to declare that the patch has been modified. As such, the user
will expect that running "git am --signoff --continue" will append the
signoff to the commit message.

However, the --signoff option is only taken into account during the
mail-parsing stage. If the --signoff option is set, then the signoff
will be appended to the commit message. Since the mail-parsing stage
comes before the patch application stage, the --signoff option, if
provided on the command-line when resuming, will have no effect at all.

We cannot move the append_signoff() call to the patch application stage
as the applypatch-msg hook and interactive mode, which run before patch
application, may expect the signoff to be there.

Fix this by taking note if the user explictly set the --signoff option
on the command-line, and append the signoff to the commit message when
resuming if so.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -98,6 +98,12 @@ enum scissors_type {
 	SCISSORS_TRUE        /* pass --scissors to git-mailinfo */
 };
 
+enum signoff_type {
+	SIGNOFF_FALSE = 0,
+	SIGNOFF_TRUE = 1,
+	SIGNOFF_EXPLICIT /* --signoff was set on the command-line */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;
@@ -123,7 +129,7 @@ struct am_state {
 	int interactive;
 	int threeway;
 	int quiet;
-	int signoff;
+	int signoff; /* enum signoff_type */
 	int utf8;
 	int keep; /* enum keep_type */
 	int message_id;
@@ -1185,6 +1191,18 @@ static void NORETURN die_user_resolve(const struct am_state *state)
 	exit(128);
 }
 
+/**
+ * Appends signoff to the "msg" field of the am_state.
+ */
+static void am_append_signoff(struct am_state *state)
+{
+	struct strbuf sb = STRBUF_INIT;
+
+	strbuf_attach(&sb, state->msg, state->msg_len, state->msg_len);
+	append_signoff(&sb, 0, 0);
+	state->msg = strbuf_detach(&sb, &state->msg_len);
+}
+
 /**
  * Parses `mail` using git-mailinfo, extracting its patch and authorship info.
  * state->msg will be set to the patch message. state->author_name,
@@ -2153,8 +2171,9 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		OPT_BOOL('3', "3way", &state.threeway,
 			N_("allow fall back on 3way merging if needed")),
 		OPT__QUIET(&state.quiet, N_("be quiet")),
-		OPT_BOOL('s', "signoff", &state.signoff,
-			N_("add a Signed-off-by line to the commit message")),
+		OPT_SET_INT('s', "signoff", &state.signoff,
+			N_("add a Signed-off-by line to the commit message"),
+			SIGNOFF_EXPLICIT),
 		OPT_BOOL('u', "utf8", &state.utf8,
 			N_("recode into utf8 (default)")),
 		OPT_SET_INT('k', "keep", &state.keep,
@@ -2267,6 +2286,9 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 
 		if (resume == RESUME_FALSE)
 			resume = RESUME_APPLY;
+
+		if (state.signoff == SIGNOFF_EXPLICIT)
+			am_append_signoff(&state);
 	} else {
 		struct argv_array paths = ARGV_ARRAY_INIT;
 		int i;

t/t4153-am-resume-override-opts.sh

@@ -64,6 +64,26 @@ test_expect_success '--no-quiet overrides --quiet' '
 	test_i18ncmp expected out
 '
 
+test_expect_success '--signoff overrides --no-signoff' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	git checkout first &&
+
+	test_must_fail git am --no-signoff side[12].eml &&
+	test_path_is_dir .git/rebase-apply &&
+	echo side1 >file &&
+	git add file &&
+	git am --signoff --continue &&
+
+	# Applied side1 will be signed off
+	echo "Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>" >expected &&
+	git cat-file commit HEAD^ | grep "Signed-off-by:" >actual &&
+	test_cmp expected actual &&
+
+	# Applied side2 will not be signed off
+	test $(git cat-file commit HEAD | grep -c "Signed-off-by:") -eq 0
+'
+
 test_expect_success TTY '--reject overrides --no-reject' '
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&