read-cache.c: write prefix-compressed names in the index

Teach the code to write the index in the v4 on-disk format.

Record the format version of the on-disk index we read from in the
index_state, and use the format when writing the new index out.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 65a7aba158..a3f1279a3e 100644
--- a/cache.h
+++ b/cache.h
@@ -105,6 +105,9 @@ struct cache_header {
 	unsigned int hdr_entries;
 };
 
+#define INDEX_FORMAT_LB 2
+#define INDEX_FORMAT_UB 4
+
 /*
  * The "cache_time" is just the low 32 bits of the
  * time. It doesn't matter if it overflows - we only
@@ -265,6 +268,7 @@ static inline unsigned int canon_mode(unsigned int mode)
 
 struct index_state {
 	struct cache_entry **cache;
+	unsigned int version;
 	unsigned int cache_nr, cache_alloc, cache_changed;
 	struct string_list *resolve_undo;
 	struct cache_tree *cache_tree;