fmt-merge-msg: don't use static buffer in record_person

The record_person function just parses out the "name" field
of the person line in a commit and adds it to a string_list.
The only reason we need an extra buffer is that the
string_list functions require a NUL-terminated string.

Instead of the static buffer, we can just allocate a
temporary NUL-terminated copy. In addition to removing a
useless limit, this removes the only user of MAX_GITNAME
outside of ident.c.

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

builtin/fmt-merge-msg.c

@@ -230,7 +230,7 @@ static void add_branch_desc(struct strbuf *out, const char *name)
 static void record_person(int which, struct string_list *people,
 			  struct commit *commit)
 {
-	char name_buf[MAX_GITNAME], *name, *name_end;
+	char *name_buf, *name, *name_end;
 	struct string_list_item *elem;
 	const char *field = (which == 'a') ? "\nauthor " : "\ncommitter ";
 
@@ -243,17 +243,17 @@ static void record_person(int which, struct string_list *people,
 		name_end--;
 	while (isspace(*name_end) && name <= name_end)
 		name_end--;
-	if (name_end < name || name + MAX_GITNAME <= name_end)
+	if (name_end < name)
 		return;
-	memcpy(name_buf, name, name_end - name + 1);
-	name_buf[name_end - name + 1] = '\0';
+	name_buf = xmemdupz(name, name_end - name + 1);
 
 	elem = string_list_lookup(people, name_buf);
 	if (!elem) {
 		elem = string_list_insert(people, name_buf);
 		elem->util = (void *)0;
 	}
 	elem->util = (void*)(util_as_integral(elem) + 1);
+	free(name_buf);
 }
 
 static int cmp_string_list_util_as_integral(const void *a_, const void *b_)