core.fsync: add a derived-metadata aggregate option

This commit adds an aggregate option that currently includes the
commit-graph file and pack metadata (indexes and bitmaps).

The user may want to exclude this set from durability since they can be
recomputed from other data if they wind up corrupt or missing.

This is split out from the other patches in the series since it is
an optional nice-to-have that might be controversial.

Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>

Author: neerajsi-msft

Documentation/config/core.txt

@@ -562,9 +562,9 @@ core.fsync::
 * `pack-metadata` hardens packfile bitmaps and indexes.
 * `commit-graph` hardens the commit graph file.
 * `index` hardens the index when it is modified.
-* `objects` is an aggregate option that includes `loose-objects`, `pack`,
-  `pack-metadata`, and `commit-graph`.
-* `default` is an aggregate option that is equivalent to `objects,-loose-object`
+* `objects` is an aggregate option that includes `loose-objects` and `pack`.
+* `derived-metadata` is an aggregate option that includes `pack-metadata` and `commit-graph`.
+* `default` is an aggregate option that is equivalent to `objects,derived-metadata,-loose-object`
 * `all` is an aggregate option that syncs all individual components above.
 
 core.fsyncMethod::

cache.h

@@ -1012,9 +1012,10 @@ enum fsync_component {
 				  FSYNC_COMPONENT_COMMIT_GRAPH)
 
 #define FSYNC_COMPONENTS_OBJECTS (FSYNC_COMPONENT_LOOSE_OBJECT | \
-				  FSYNC_COMPONENT_PACK | \
-				  FSYNC_COMPONENT_PACK_METADATA | \
-				  FSYNC_COMPONENT_COMMIT_GRAPH)
+				  FSYNC_COMPONENT_PACK)
+
+#define FSYNC_COMPONENTS_DERIVED_METADATA (FSYNC_COMPONENT_PACK_METADATA | \
+					   FSYNC_COMPONENT_COMMIT_GRAPH)
 
 #define FSYNC_COMPONENTS_ALL (FSYNC_COMPONENT_LOOSE_OBJECT | \
 			      FSYNC_COMPONENT_PACK | \

config.c

@@ -1223,6 +1223,7 @@ static const struct fsync_component_entry {
 	{ "commit-graph", FSYNC_COMPONENT_COMMIT_GRAPH },
 	{ "index", FSYNC_COMPONENT_INDEX },
 	{ "objects", FSYNC_COMPONENTS_OBJECTS },
+	{ "derived-metadata", FSYNC_COMPONENTS_DERIVED_METADATA },
 	{ "default", FSYNC_COMPONENTS_DEFAULT },
 	{ "all", FSYNC_COMPONENTS_ALL },
 };