builtin-branch: use strbuf in fill_tracking_info()

This is just about using the API, though in case of ~ 10^100 commits,
this would fix the problem of writing to unallocated memory as well. ;-)

Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-branch.c

@@ -279,19 +279,19 @@ static int ref_cmp(const void *r1, const void *r2)
 	return strcmp(c1->name, c2->name);
 }
 
-static void fill_tracking_info(char *stat, const char *branch_name)
+static void fill_tracking_info(struct strbuf *stat, const char *branch_name)
 {
 	int ours, theirs;
 	struct branch *branch = branch_get(branch_name);
 
 	if (!stat_tracking_info(branch, &ours, &theirs) || (!ours && !theirs))
 		return;
 	if (!ours)
-		sprintf(stat, "[behind %d] ", theirs);
+		strbuf_addf(stat, "[behind %d] ", theirs);
 	else if (!theirs)
-		sprintf(stat, "[ahead %d] ", ours);
+		strbuf_addf(stat, "[ahead %d] ", ours);
 	else
-		sprintf(stat, "[ahead %d, behind %d] ", ours, theirs);
+		strbuf_addf(stat, "[ahead %d, behind %d] ", ours, theirs);
 }
 
 static int matches_merge_filter(struct commit *commit)
@@ -334,11 +334,8 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 	}
 
 	if (verbose) {
-		struct strbuf subject = STRBUF_INIT;
+		struct strbuf subject = STRBUF_INIT, stat = STRBUF_INIT;
 		const char *sub = " **** invalid ref ****";
-		char stat[128];
-
-		stat[0] = '\0';
 
 		commit = item->commit;
 		if (commit && !parse_commit(commit)) {
@@ -348,13 +345,14 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 		}
 
 		if (item->kind == REF_LOCAL_BRANCH)
-			fill_tracking_info(stat, item->name);
+			fill_tracking_info(&stat, item->name);
 
 		printf("%c %s%-*s%s %s %s%s\n", c, branch_get_color(color),
 		       maxwidth, item->name,
 		       branch_get_color(COLOR_BRANCH_RESET),
 		       find_unique_abbrev(item->commit->object.sha1, abbrev),
-		       stat, sub);
+		       stat.buf, sub);
+		strbuf_release(&stat);
 		strbuf_release(&subject);
 	} else {
 		printf("%c %s%s%s\n", c, branch_get_color(color), item->name,