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.h

@@ -187,6 +187,16 @@ extern int repo_config_get_maybe_bool(struct repository *repo,
 extern int repo_config_get_pathname(struct repository *repo,
 				    const char *key, const char **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.
+ */
+extern void config_from_gitmodules(config_fn_t fn, void *data);
+
 extern int git_config_get_value(const char *key, const char **value);
 extern const struct string_list *git_config_get_value_multi(const char *key);
 extern void git_config_clear(void);