Merge branch 'mh/shorten-unambigous-ref'

* mh/shorten-unambigous-ref:
  shorten_unambiguous_ref(): tighten up pointer arithmetic
  gen_scanf_fmt(): delete function and use snprintf() instead
  shorten_unambiguous_ref(): introduce a new local variable

Author: gitster

refs.c

@@ -3334,53 +3334,36 @@ int update_refs(const char *action, const struct ref_update **updates_orig,
 	return ret;
 }
 
-/*
- * generate a format suitable for scanf from a ref_rev_parse_rules
- * rule, that is replace the "%.*s" spec with a "%s" spec
- */
-static void gen_scanf_fmt(char *scanf_fmt, const char *rule)
-{
-	char *spec;
-
-	spec = strstr(rule, "%.*s");
-	if (!spec || strstr(spec + 4, "%.*s"))
-		die("invalid rule in ref_rev_parse_rules: %s", rule);
-
-	/* copy all until spec */
-	strncpy(scanf_fmt, rule, spec - rule);
-	scanf_fmt[spec - rule] = '\0';
-	/* copy new spec */
-	strcat(scanf_fmt, "%s");
-	/* copy remaining rule */
-	strcat(scanf_fmt, spec + 4);
-
-	return;
-}
-
 char *shorten_unambiguous_ref(const char *refname, int strict)
 {
 	int i;
 	static char **scanf_fmts;
 	static int nr_rules;
 	char *short_name;
 
-	/* pre generate scanf formats from ref_rev_parse_rules[] */
 	if (!nr_rules) {
+		/*
+		 * Pre-generate scanf formats from ref_rev_parse_rules[].
+		 * Generate a format suitable for scanf from a
+		 * ref_rev_parse_rules rule by interpolating "%s" at the
+		 * location of the "%.*s".
+		 */
 		size_t total_len = 0;
+		size_t offset = 0;
 
 		/* the rule list is NULL terminated, count them first */
 		for (nr_rules = 0; ref_rev_parse_rules[nr_rules]; nr_rules++)
-			/* no +1 because strlen("%s") < strlen("%.*s") */
-			total_len += strlen(ref_rev_parse_rules[nr_rules]);
+			/* -2 for strlen("%.*s") - strlen("%s"); +1 for NUL */
+			total_len += strlen(ref_rev_parse_rules[nr_rules]) - 2 + 1;
 
 		scanf_fmts = xmalloc(nr_rules * sizeof(char *) + total_len);
 
-		total_len = 0;
+		offset = 0;
 		for (i = 0; i < nr_rules; i++) {
-			scanf_fmts[i] = (char *)&scanf_fmts[nr_rules]
-					+ total_len;
-			gen_scanf_fmt(scanf_fmts[i], ref_rev_parse_rules[i]);
-			total_len += strlen(ref_rev_parse_rules[i]);
+			assert(offset < total_len);
+			scanf_fmts[i] = (char *)&scanf_fmts[nr_rules] + offset;
+			offset += snprintf(scanf_fmts[i], total_len - offset,
+					   ref_rev_parse_rules[i], 2, "%s") + 1;
 		}
 	}