dir: add remove_untracked_cache()

Factor out code into remove_untracked_cache(), which will be used
in a later commit.
Signed-off-by: NChristian Couder <chriscool@tuxfamily.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/update-index.c

@@ -1126,11 +1126,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 		add_untracked_cache(&the_index);
 		report(_("Untracked cache enabled for '%s'"), get_git_work_tree());
 	} else if (untracked_cache == UC_DISABLE) {
-		if (the_index.untracked) {
-			free_untracked_cache(the_index.untracked);
-			the_index.untracked = NULL;
-			the_index.cache_changed |= UNTRACKED_CHANGED;
-		}
+		remove_untracked_cache(&the_index);
 		report(_("Untracked cache disabled"));
 	}
 

dir.c

@@ -1956,6 +1956,15 @@ void add_untracked_cache(struct index_state *istate)
 	istate->cache_changed |= UNTRACKED_CHANGED;
 }
 
+void remove_untracked_cache(struct index_state *istate)
+{
+	if (istate->untracked) {
+		free_untracked_cache(istate->untracked);
+		istate->untracked = NULL;
+		istate->cache_changed |= UNTRACKED_CHANGED;
+	}
+}
+
 static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *dir,
 						      int base_len,
 						      const struct pathspec *pathspec)

dir.h

@@ -309,4 +309,5 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 void write_untracked_extension(struct strbuf *out, struct untracked_cache *untracked);
 void add_untracked_ident(struct untracked_cache *);
 void add_untracked_cache(struct index_state *istate);
+void remove_untracked_cache(struct index_state *istate);
 #endif