git-shortlog: make common repository prefix configurable with .mailmap

The code had "/pub/scm/linux/kernel/git/" hardcoded which was
too specific to the kernel project.

With this, a line in the .mailmap file:

	# repo-abbrev: /pub/scm/linux/kernel/git/

can be used to cause the substring to be abbreviated to /.../
on the title line of the commit message.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-shortlog.c

@@ -9,6 +9,8 @@
 static const char shortlog_usage[] =
 "git-shortlog [-n] [-s] [<commit-id>... ]";
 
+static char *common_repo_prefix;
+
 static int compare_by_number(const void *a1, const void *a2)
 {
 	const struct path_list_item *i1 = a1, *i2 = a2;
@@ -35,8 +37,26 @@ static int read_mailmap(const char *filename)
 		char *end_of_name, *left_bracket, *right_bracket;
 		char *name, *email;
 		int i;
-		if (buffer[0] == '#')
+		if (buffer[0] == '#') {
+			static const char abbrev[] = "# repo-abbrev:";
+			int abblen = sizeof(abbrev) - 1;
+			int len = strlen(buffer);
+
+			if (len && buffer[len - 1] == '\n')
+				buffer[--len] = 0;
+			if (!strncmp(buffer, abbrev, abblen)) {
+				char *cp;
+
+				if (common_repo_prefix)
+					free(common_repo_prefix);
+				common_repo_prefix = xmalloc(len);
+
+				for (cp = buffer + abblen; isspace(*cp); cp++)
+					; /* nothing */
+				strcpy(common_repo_prefix, cp);
+			}
 			continue;
+		}
 		if ((left_bracket = strchr(buffer, '<')) == NULL)
 			continue;
 		if ((right_bracket = strchr(left_bracket + 1, '>')) == NULL)
@@ -87,7 +107,7 @@ static void insert_author_oneline(struct path_list *list,
 		const char *author, int authorlen,
 		const char *oneline, int onelinelen)
 {
-	const char *dot3 = "/pub/scm/linux/kernel/git/";
+	const char *dot3 = common_repo_prefix;
 	char *buffer, *p;
 	struct path_list_item *item;
 	struct path_list *onelines;

contrib/mailmap.linux

@@ -3,6 +3,8 @@
 # So have an email->real name table to translate the
 # (hopefully few) missing names
 #
+# repo-abbrev: /pub/scm/linux/kernel/git/
+#
 Adrian Bunk <bunk@stusta.de>
 Andreas Herrmann <aherrman@de.ibm.com>
 Andrew Morton <akpm@osdl.org>