extern int trust_executable_bit;
 extern int assume_unchanged;
 extern int only_use_symrefs;
+extern int warn_ambiguous_refs;
 extern int diff_rename_limit_default;
 extern int shared_repository;
 extern const char *apply_default_whitespace;
 
                return 0;
        }
 
+       if (!strcmp(var, "core.warnambiguousrefs")) {
+               warn_ambiguous_refs = git_config_bool(var, value);
+               return 0;
+       }
+
        if (!strcmp(var, "user.name")) {
                strncpy(git_default_name, value, sizeof(git_default_name));
                return 0;
 
 int trust_executable_bit = 1;
 int assume_unchanged = 0;
 int only_use_symrefs = 0;
+int warn_ambiguous_refs = 0;
 int repository_format_version = 0;
 char git_commit_encoding[MAX_ENCODING_LENGTH] = "utf-8";
 int shared_repository = 0;
 
                "refs",
                "refs/tags",
                "refs/heads",
+               "refs/remotes",
                NULL
        };
        const char **p;
+       const char *warning = "warning: refname '%.*s' is ambiguous.\n";
+       char *pathname;
+       int already_found = 0;
 
        if (len == 40 && !get_sha1_hex(str, sha1))
                return 0;
                return -1;
 
        for (p = prefix; *p; p++) {
-               char *pathname = git_path("%s/%.*s", *p, len, str);
-               if (!read_ref(pathname, sha1))
-                       return 0;
+               unsigned char sha1_from_ref[20];
+               unsigned char *this_result =
+                       already_found ? sha1_from_ref : sha1;
+               pathname = git_path("%s/%.*s", *p, len, str);
+               if (!read_ref(pathname, this_result)) {
+                       if (warn_ambiguous_refs) {
+                               if (already_found &&
+                                   !memcmp(sha1, sha1_from_ref, 20))
+                                       fprintf(stderr, warning, len, str);
+                               already_found++;
+                       }
+                       else
+                               return 0;
+               }
        }
+       if (already_found)
+               return 0;
        return -1;
 }