i18n: git-commit whence_s "merge/cherry-pick" message

Mark the "merge/cherry-pick" messages in whence_s for translation.
These messages returned from whence_s function are used as argument
to build other messages.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -196,16 +196,16 @@ static void determine_whence(struct wt_status *s)
 
 static const char *whence_s(void)
 {
-	char *s = "";
+	const char *s = "";
 
 	switch (whence) {
 	case FROM_COMMIT:
 		break;
 	case FROM_MERGE:
-		s = "merge";
+		s = _("merge");
 		break;
 	case FROM_CHERRY_PICK:
-		s = "cherry-pick";
+		s = _("cherry-pick");
 		break;
 	}