Merge branch 'bw/grep-recurse-submodules'

"git grep --recurse-submodules" has been reworked to give a more
consistent output across submodule boundary (and do its thing
without having to fork a separate process).

* bw/grep-recurse-submodules:
  grep: recurse in-process using 'struct repository'
  submodule: merge repo_read_gitmodules and gitmodules_config
  submodule: check for unmerged .gitmodules outside of config parsing
  submodule: check for unstaged .gitmodules outside of config parsing
  submodule: remove fetch.recursesubmodules from submodule-config parsing
  submodule: remove submodule.fetchjobs from submodule-config parsing
  config: add config_from_gitmodules
  cache.h: add GITMODULES_FILE macro
  repository: have the_repository use the_index
  repo_read_index: don't discard the index

config.c

@@ -2059,6 +2059,23 @@ int git_config_get_pathname(const char *key, const char **dest)
 	return repo_config_get_pathname(the_repository, key, dest);
 }
 
+/*
+ * Note: This function exists solely to maintain backward compatibility with
+ * 'fetch' and 'update_clone' storing configuration in '.gitmodules' and should
+ * NOT be used anywhere else.
+ *
+ * Runs the provided config function on the '.gitmodules' file found in the
+ * working directory.
+ */
+void config_from_gitmodules(config_fn_t fn, void *data)
+{
+	if (the_repository->worktree) {
+		char *file = repo_worktree_path(the_repository, GITMODULES_FILE);
+		git_config_from_file(fn, file, data);
+		free(file);
+	}
+}
+
 int git_config_get_expiry(const char *key, const char **output)
 {
 	int ret = git_config_get_string_const(key, output);