ref-filter: drop sprintf and strcpy calls

The ref-filter code comes from for-each-ref, and inherited a
number of raw sprintf and strcpy calls. These are generally
all safe, as we custom-size the buffers, or are formatting
numbers into sufficiently large buffers. But we can make the
resulting code even simpler and more obviously correct by
using some of our helper functions.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

ref-filter.c

@@ -192,9 +192,7 @@ static int grab_objectname(const char *name, const unsigned char *sha1,
 			    struct atom_value *v)
 {
 	if (!strcmp(name, "objectname")) {
-		char *s = xmalloc(41);
-		strcpy(s, sha1_to_hex(sha1));
-		v->s = s;
+		v->s = xstrdup(sha1_to_hex(sha1));
 		return 1;
 	}
 	if (!strcmp(name, "objectname:short")) {
@@ -219,10 +217,8 @@ static void grab_common_values(struct atom_value *val, int deref, struct object
 		if (!strcmp(name, "objecttype"))
 			v->s = typename(obj->type);
 		else if (!strcmp(name, "objectsize")) {
-			char *s = xmalloc(40);
-			sprintf(s, "%lu", sz);
 			v->ul = sz;
-			v->s = s;
+			v->s = xstrfmt("%lu", sz);
 		}
 		else if (deref)
 			grab_objectname(name, obj->sha1, v);
@@ -246,11 +242,8 @@ static void grab_tag_values(struct atom_value *val, int deref, struct object *ob
 			v->s = tag->tag;
 		else if (!strcmp(name, "type") && tag->tagged)
 			v->s = typename(tag->tagged->type);
-		else if (!strcmp(name, "object") && tag->tagged) {
-			char *s = xmalloc(41);
-			strcpy(s, sha1_to_hex(tag->tagged->sha1));
-			v->s = s;
-		}
+		else if (!strcmp(name, "object") && tag->tagged)
+			v->s = xstrdup(sha1_to_hex(tag->tagged->sha1));
 	}
 }
 
@@ -268,32 +261,22 @@ static void grab_commit_values(struct atom_value *val, int deref, struct object
 		if (deref)
 			name++;
 		if (!strcmp(name, "tree")) {
-			char *s = xmalloc(41);
-			strcpy(s, sha1_to_hex(commit->tree->object.sha1));
-			v->s = s;
+			v->s = xstrdup(sha1_to_hex(commit->tree->object.sha1));
 		}
-		if (!strcmp(name, "numparent")) {
-			char *s = xmalloc(40);
+		else if (!strcmp(name, "numparent")) {
 			v->ul = commit_list_count(commit->parents);
-			sprintf(s, "%lu", v->ul);
-			v->s = s;
+			v->s = xstrfmt("%lu", v->ul);
 		}
 		else if (!strcmp(name, "parent")) {
-			int num = commit_list_count(commit->parents);
-			int i;
 			struct commit_list *parents;
-			char *s = xmalloc(41 * num + 1);
-			v->s = s;
-			for (i = 0, parents = commit->parents;
-			     parents;
-			     parents = parents->next, i = i + 41) {
+			struct strbuf s = STRBUF_INIT;
+			for (parents = commit->parents; parents; parents = parents->next) {
 				struct commit *parent = parents->item;
-				strcpy(s+i, sha1_to_hex(parent->object.sha1));
-				if (parents->next)
-					s[i+40] = ' ';
+				if (parents != commit->parents)
+					strbuf_addch(&s, ' ');
+				strbuf_addstr(&s, sha1_to_hex(parent->object.sha1));
 			}
-			if (!i)
-				*s = '\0';
+			v->s = strbuf_detach(&s, NULL);
 		}
 	}
 }
@@ -700,7 +683,6 @@ static void populate_value(struct ref_array_item *ref)
 			else if (!strcmp(formatp, "track") &&
 				 (starts_with(name, "upstream") ||
 				  starts_with(name, "push"))) {
-				char buf[40];
 
 				if (stat_tracking_info(branch, &num_ours,
 						       &num_theirs, NULL))
@@ -708,17 +690,13 @@ static void populate_value(struct ref_array_item *ref)
 
 				if (!num_ours && !num_theirs)
 					v->s = "";
-				else if (!num_ours) {
-					sprintf(buf, "[behind %d]", num_theirs);
-					v->s = xstrdup(buf);
-				} else if (!num_theirs) {
-					sprintf(buf, "[ahead %d]", num_ours);
-					v->s = xstrdup(buf);
-				} else {
-					sprintf(buf, "[ahead %d, behind %d]",
-						num_ours, num_theirs);
-					v->s = xstrdup(buf);
-				}
+				else if (!num_ours)
+					v->s = xstrfmt("[behind %d]", num_theirs);
+				else if (!num_theirs)
+					v->s = xstrfmt("[ahead %d]", num_ours);
+				else
+					v->s = xstrfmt("[ahead %d, behind %d]",
+						       num_ours, num_theirs);
 				continue;
 			} else if (!strcmp(formatp, "trackshort") &&
 				   (starts_with(name, "upstream") ||
@@ -745,12 +723,8 @@ static void populate_value(struct ref_array_item *ref)
 
 		if (!deref)
 			v->s = refname;
-		else {
-			int len = strlen(refname);
-			char *s = xmalloc(len + 4);
-			sprintf(s, "%s^{}", refname);
-			v->s = s;
-		}
+		else
+			v->s = xstrfmt("%s^{}", refname);
 	}
 
 	for (i = 0; i < used_atom_cnt; i++) {