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

diff --combined refs.c
index 39261368f5656273b0910c5b61a58d215afbcc5d,676bfd550e742b87cae0f6cbbd6fa6e7e643057a..490b57b881d88f3f88b11327b20d19f6f3938c46
--- 1/refs.c
--- 2/refs.c
+++ b/refs.c
@@@ -637,7 -637,7 +637,7 @@@ static int do_one_ref(struct ref_entry 
        struct ref_entry *old_current_ref;
        int retval;
  
 -      if (prefixcmp(entry->name, data->base))
 +      if (!starts_with(entry->name, data->base))
                return 0;
  
        if (!(data->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
@@@ -1042,7 -1042,7 +1042,7 @@@ static void read_packed_refs(FILE *f, s
                if (refname) {
                        last = create_ref_entry(refname, sha1, REF_ISPACKED, 1);
                        if (peeled == PEELED_FULLY ||
 -                          (peeled == PEELED_TAGS && !prefixcmp(refname, "refs/tags/")))
 +                          (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
                                last->flag |= REF_KNOWS_PEELED;
                        add_ref(dir, last);
                        continue;
@@@ -1376,7 -1376,7 +1376,7 @@@ const char *resolve_ref_unsafe(const ch
                                        return NULL;
                        }
                        buffer[len] = 0;
 -                      if (!prefixcmp(buffer, "refs/") &&
 +                      if (starts_with(buffer, "refs/") &&
                                        !check_refname_format(buffer, 0)) {
                                strcpy(refname_buffer, buffer);
                                refname = refname_buffer;
@@@ -1415,7 -1415,7 +1415,7 @@@
                /*
                 * Is it a symbolic ref?
                 */
 -              if (prefixcmp(buffer, "ref:")) {
 +              if (!starts_with(buffer, "ref:")) {
                        /*
                         * Please note that FETCH_HEAD has a second
                         * line containing other data.
@@@ -1837,7 -1837,7 +1837,7 @@@ int for_each_glob_ref_in(each_ref_fn fn
        struct ref_filter filter;
        int ret;
  
 -      if (!prefix && prefixcmp(pattern, "refs/"))
 +      if (!prefix && !starts_with(pattern, "refs/"))
                strbuf_addstr(&real_pattern, "refs/");
        else if (prefix)
                strbuf_addstr(&real_pattern, prefix);
@@@ -1874,9 -1874,9 +1874,9 @@@ int for_each_rawref(each_ref_fn fn, voi
  const char *prettify_refname(const char *name)
  {
        return name + (
 -              !prefixcmp(name, "refs/heads/") ? 11 :
 -              !prefixcmp(name, "refs/tags/") ? 10 :
 -              !prefixcmp(name, "refs/remotes/") ? 13 :
 +              starts_with(name, "refs/heads/") ? 11 :
 +              starts_with(name, "refs/tags/") ? 10 :
 +              starts_with(name, "refs/remotes/") ? 13 :
                0);
  }
  
@@@ -2244,7 -2244,7 +2244,7 @@@ static int pack_if_possible_fn(struct r
        struct pack_refs_cb_data *cb = cb_data;
        enum peel_status peel_status;
        struct ref_entry *packed_entry;
 -      int is_tag_ref = !prefixcmp(entry->name, "refs/tags/");
 +      int is_tag_ref = starts_with(entry->name, "refs/tags/");
  
        /* ALWAYS pack tags */
        if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
@@@ -2679,9 -2679,9 +2679,9 @@@ int log_ref_setup(const char *refname, 
  
        git_snpath(logfile, bufsize, "logs/%s", refname);
        if (log_all_ref_updates &&
 -          (!prefixcmp(refname, "refs/heads/") ||
 -           !prefixcmp(refname, "refs/remotes/") ||
 -           !prefixcmp(refname, "refs/notes/") ||
 +          (starts_with(refname, "refs/heads/") ||
 +           starts_with(refname, "refs/remotes/") ||
 +           starts_with(refname, "refs/notes/") ||
             !strcmp(refname, "HEAD"))) {
                if (safe_create_leading_directories(logfile) < 0)
                        return error("unable to create directory for %s",
@@@ -2751,7 -2751,7 +2751,7 @@@ static int log_ref_write(const char *re
  
  static int is_branch(const char *refname)
  {
 -      return !strcmp(refname, "HEAD") || !prefixcmp(refname, "refs/heads/");
 +      return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
  }
  
  int write_ref_sha1(struct ref_lock *lock,
@@@ -3334,29 -3334,6 +3334,6 @@@ cleanup
        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;
@@@ -3364,23 -3341,29 +3341,29 @@@
        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;
                }
        }
  
@@@ -3450,7 -3433,7 +3433,7 @@@ int parse_hide_refs_config(const char *
  {
        if (!strcmp("transfer.hiderefs", var) ||
            /* NEEDSWORK: use parse_config_key() once both are merged */
 -          (!prefixcmp(var, section) && var[strlen(section)] == '.' &&
 +          (starts_with(var, section) && var[strlen(section)] == '.' &&
             !strcmp(var + strlen(section), ".hiderefs"))) {
                char *ref;
                int len;
@@@ -3478,7 -3461,7 +3461,7 @@@ int ref_is_hidden(const char *refname
                return 0;
        for_each_string_list_item(item, hide_refs) {
                int len;
 -              if (prefixcmp(refname, item->string))
 +              if (!starts_with(refname, item->string))
                        continue;
                len = strlen(item->string);
                if (!refname[len] || refname[len] == '/')