introduce "extensions" form of core.repositoryformatversion

diff --git a/cache.h b/cache.h
index 4f554664c5bd064405082797ee1e8786ebdcea75..996584c1ceaced7a8be6d03c684c94e9272fa1fe 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -686,7 +686,13 @@ extern char *notes_ref_name;
 
 extern int grafts_replace_parents;
 
+/*
+ * GIT_REPO_VERSION is the version we write by default. The
+ * _READ variant is the highest number we know how to
+ * handle.
+ */
 #define GIT_REPO_VERSION 0
+#define GIT_REPO_VERSION_READ 1
 extern int repository_format_version;
 extern int check_repository_format(void);