sequencer.c: teach append_signoff how to detect duplicate s-o-b

Teach append_signoff how to detect a duplicate s-o-b in the commit footer.
This is in preparation to unify the append_signoff implementations in
log-tree.c and sequencer.c.

Fixes test in t3511.

Signed-off-by: Brandon Casey <bcasey@nvidia.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -700,7 +700,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 			previous = eol;
 		}
 
-		append_signoff(&sb, ignore_footer);
+		append_signoff(&sb, ignore_footer, 0);
 	}
 
 	if (fwrite(sb.buf, 1, sb.len, s->fp) < sb.len)

sequencer.c

@@ -44,12 +44,20 @@ static int is_cherry_picked_from_line(const char *buf, int len)
 		!prefixcmp(buf, cherry_picked_prefix) && buf[len - 1] == ')';
 }
 
-static int has_conforming_footer(struct strbuf *sb, int ignore_footer)
+/*
+ * Returns 0 for non-conforming footer
+ * Returns 1 for conforming footer
+ * Returns 2 when sob exists within conforming footer
+ * Returns 3 when sob exists within conforming footer as last entry
+ */
+static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
+	int ignore_footer)
 {
 	char prev;
 	int i, k;
 	int len = sb->len - ignore_footer;
 	const char *buf = sb->buf;
+	int found_sob = 0;
 
 	/* footer must end with newline */
 	if (!len || buf[len - 1] != '\n')
@@ -72,14 +80,25 @@ static int has_conforming_footer(struct strbuf *sb, int ignore_footer)
 		i++;
 
 	for (; i < len; i = k) {
+		int found_rfc2822;
+
 		for (k = i; k < len && buf[k] != '\n'; k++)
 			; /* do nothing */
 		k++;
 
-		if (!is_rfc2822_line(buf + i, k - i - 1) &&
-		    !is_cherry_picked_from_line(buf + i, k - i - 1))
+		found_rfc2822 = is_rfc2822_line(buf + i, k - i - 1);
+		if (found_rfc2822 && sob &&
+		    !strncmp(buf + i, sob->buf, sob->len))
+			found_sob = k;
+
+		if (!(found_rfc2822 ||
+		      is_cherry_picked_from_line(buf + i, k - i - 1)))
 			return 0;
 	}
+	if (found_sob == i)
+		return 3;
+	if (found_sob)
+		return 2;
 	return 1;
 }
 
@@ -300,7 +319,7 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 	rollback_lock_file(&index_lock);
 
 	if (opts->signoff)
-		append_signoff(msgbuf, 0);
+		append_signoff(msgbuf, 0, 0);
 
 	if (!clean) {
 		int i;
@@ -556,7 +575,7 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 		}
 
 		if (opts->record_origin) {
-			if (!has_conforming_footer(&msgbuf, 0))
+			if (!has_conforming_footer(&msgbuf, NULL, 0))
 				strbuf_addch(&msgbuf, '\n');
 			strbuf_addstr(&msgbuf, cherry_picked_prefix);
 			strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
@@ -1083,21 +1102,33 @@ int sequencer_pick_revisions(struct replay_opts *opts)
 	return pick_commits(todo_list, opts);
 }
 
-void append_signoff(struct strbuf *msgbuf, int ignore_footer)
+void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag)
 {
+	unsigned no_dup_sob = flag & APPEND_SIGNOFF_DEDUP;
 	struct strbuf sob = STRBUF_INIT;
-	int i;
+	int has_footer;
 
 	strbuf_addstr(&sob, sign_off_header);
 	strbuf_addstr(&sob, fmt_name(getenv("GIT_COMMITTER_NAME"),
 				getenv("GIT_COMMITTER_EMAIL")));
 	strbuf_addch(&sob, '\n');
-	for (i = msgbuf->len - 1 - ignore_footer; i > 0 && msgbuf->buf[i - 1] != '\n'; i--)
-		; /* do nothing */
-	if (prefixcmp(msgbuf->buf + i, sob.buf)) {
-		if (!has_conforming_footer(msgbuf, ignore_footer))
+
+	/*
+	 * If the whole message buffer is equal to the sob, pretend that we
+	 * found a conforming footer with a matching sob
+	 */
+	if (msgbuf->len - ignore_footer == sob.len &&
+	    !strncmp(msgbuf->buf, sob.buf, sob.len))
+		has_footer = 3;
+	else
+		has_footer = has_conforming_footer(msgbuf, &sob, ignore_footer);
+
+	if (!has_footer)
 		strbuf_splice(msgbuf, msgbuf->len - ignore_footer, 0, "\n", 1);
-		strbuf_splice(msgbuf, msgbuf->len - ignore_footer, 0, sob.buf, sob.len);
-	}
+
+	if (has_footer != 3 && (!no_dup_sob || has_footer != 2))
+		strbuf_splice(msgbuf, msgbuf->len - ignore_footer, 0,
+				sob.buf, sob.len);
+
 	strbuf_release(&sob);
 }

sequencer.h

@@ -6,6 +6,8 @@
 #define SEQ_TODO_FILE	"sequencer/todo"
 #define SEQ_OPTS_FILE	"sequencer/opts"
 
+#define APPEND_SIGNOFF_DEDUP (1u << 0)
+
 enum replay_action {
 	REPLAY_REVERT,
 	REPLAY_PICK
@@ -48,6 +50,6 @@ int sequencer_pick_revisions(struct replay_opts *opts);
 
 extern const char sign_off_header[];
 
-void append_signoff(struct strbuf *msgbuf, int ignore_footer);
+void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag);
 
 #endif

t/t3511-cherry-pick-x.sh

@@ -82,7 +82,7 @@ test_expect_success 'cherry-pick -s inserts blank line after one line subject' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'cherry-pick -s inserts blank line after non-conforming footer' '
+test_expect_success 'cherry-pick -s inserts blank line after non-conforming footer' '
 	pristine_detach initial &&
 	git cherry-pick -s mesg-broken-footer &&
 	cat <<-EOF >expect &&