shortlog: optimize out useless "<none>" normalization

If we are in --summary mode, we will always pass <none> to
insert_one_record, which will then do some normalization
(e.g., cutting out "[PATCH]"). There's no point in doing so
if we aren't going to use the result anyway.

This drops my best-of-five for "git shortlog -ns HEAD" on
linux.git from:

  real    0m5.257s
  user    0m5.104s
  sys     0m0.156s

to:

  real    0m5.194s
  user    0m5.028s
  sys     0m0.168s

That's only 1%, but arguably the result is clearer to read,
as we're able to group our variable declarations inside the
conditional block. It also opens up further optimization
possibilities for future patches.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/shortlog.c

@@ -31,13 +31,9 @@ static void insert_one_record(struct shortlog *log,
 			      const char *author,
 			      const char *oneline)
 {
-	const char *dot3 = log->common_repo_prefix;
-	char *buffer, *p;
 	struct string_list_item *item;
 	const char *mailbuf, *namebuf;
 	size_t namelen, maillen;
-	const char *eol;
-	struct strbuf subject = STRBUF_INIT;
 	struct strbuf namemailbuf = STRBUF_INIT;
 	struct ident_split ident;
 
@@ -59,34 +55,43 @@ static void insert_one_record(struct shortlog *log,
 	if (item->util == NULL)
 		item->util = xcalloc(1, sizeof(struct string_list));
 
-	/* Skip any leading whitespace, including any blank lines. */
-	while (*oneline && isspace(*oneline))
-		oneline++;
-	eol = strchr(oneline, '\n');
-	if (!eol)
-		eol = oneline + strlen(oneline);
-	if (starts_with(oneline, "[PATCH")) {
-		char *eob = strchr(oneline, ']');
-		if (eob && (!eol || eob < eol))
-			oneline = eob + 1;
-	}
-	while (*oneline && isspace(*oneline) && *oneline != '\n')
-		oneline++;
-	format_subject(&subject, oneline, " ");
-	buffer = strbuf_detach(&subject, NULL);
+	if (log->summary)
+		string_list_append(item->util, xstrdup(""));
+	else {
+		const char *dot3 = log->common_repo_prefix;
+		char *buffer, *p;
+		struct strbuf subject = STRBUF_INIT;
+		const char *eol;
 
-	if (dot3) {
-		int dot3len = strlen(dot3);
-		if (dot3len > 5) {
-			while ((p = strstr(buffer, dot3)) != NULL) {
-				int taillen = strlen(p) - dot3len;
-				memcpy(p, "/.../", 5);
-				memmove(p + 5, p + dot3len, taillen + 1);
+		/* Skip any leading whitespace, including any blank lines. */
+		while (*oneline && isspace(*oneline))
+			oneline++;
+		eol = strchr(oneline, '\n');
+		if (!eol)
+			eol = oneline + strlen(oneline);
+		if (starts_with(oneline, "[PATCH")) {
+			char *eob = strchr(oneline, ']');
+			if (eob && (!eol || eob < eol))
+				oneline = eob + 1;
+		}
+		while (*oneline && isspace(*oneline) && *oneline != '\n')
+			oneline++;
+		format_subject(&subject, oneline, " ");
+		buffer = strbuf_detach(&subject, NULL);
+
+		if (dot3) {
+			int dot3len = strlen(dot3);
+			if (dot3len > 5) {
+				while ((p = strstr(buffer, dot3)) != NULL) {
+					int taillen = strlen(p) - dot3len;
+					memcpy(p, "/.../", 5);
+					memmove(p + 5, p + dot3len, taillen + 1);
+				}
 			}
 		}
-	}
 
-	string_list_append(item->util, buffer);
+		string_list_append(item->util, buffer);
+	}
 }
 
 static void read_from_stdin(struct shortlog *log)