core.fsync: new option to harden the index

This commit introduces the new ability for the user to harden
the index. In the event of a system crash, the index must be
durable for the user to actually find a file that has been added
to the repo and then deleted from the working tree.

We use the presence of the COMMIT_LOCK flag and absence of the
alternate_index_output as a proxy for determining whether we're
updating the persistent index of the repo or some temporary
index. We don't sync these temporary indexes.

Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 7ac1959258..e08eeac6c1 100644
--- a/cache.h
+++ b/cache.h
@@ -1004,6 +1004,7 @@ enum fsync_component {
 	FSYNC_COMPONENT_PACK			= 1 << 1,
 	FSYNC_COMPONENT_PACK_METADATA		= 1 << 2,
 	FSYNC_COMPONENT_COMMIT_GRAPH		= 1 << 3,
+	FSYNC_COMPONENT_INDEX			= 1 << 4,
 };
 
 #define FSYNC_COMPONENTS_DEFAULT (FSYNC_COMPONENT_PACK | \