Merge branch 'ps/fsync-refs'

Updates to refs traditionally weren't fsync'ed, but we can
configure using core.fsync variable to do so.

* ps/fsync-refs:
  core.fsync: new option to harden references

Author: gitster

Documentation/config/core.txt

@@ -575,6 +575,7 @@ but risks losing recent work in the event of an unclean system shutdown.
 * `index` hardens the index when it is modified.
 * `objects` is an aggregate option that is equivalent to
   `loose-object,pack`.
+* `reference` hardens references modified in the repo.
 * `derived-metadata` is an aggregate option that is equivalent to
   `pack-metadata,commit-graph`.
 * `committed` is an aggregate option that is currently equivalent to

cache.h

@@ -1005,6 +1005,7 @@ enum fsync_component {
 	FSYNC_COMPONENT_PACK_METADATA		= 1 << 2,
 	FSYNC_COMPONENT_COMMIT_GRAPH		= 1 << 3,
 	FSYNC_COMPONENT_INDEX			= 1 << 4,
+	FSYNC_COMPONENT_REFERENCE		= 1 << 5,
 };
 
 #define FSYNC_COMPONENTS_OBJECTS (FSYNC_COMPONENT_LOOSE_OBJECT | \
@@ -1017,7 +1018,8 @@ enum fsync_component {
 				  FSYNC_COMPONENTS_DERIVED_METADATA | \
 				  ~FSYNC_COMPONENT_LOOSE_OBJECT)
 
-#define FSYNC_COMPONENTS_COMMITTED (FSYNC_COMPONENTS_OBJECTS)
+#define FSYNC_COMPONENTS_COMMITTED (FSYNC_COMPONENTS_OBJECTS | \
+				    FSYNC_COMPONENT_REFERENCE)
 
 #define FSYNC_COMPONENTS_ADDED (FSYNC_COMPONENTS_COMMITTED | \
 				FSYNC_COMPONENT_INDEX)
@@ -1026,7 +1028,8 @@ enum fsync_component {
 			      FSYNC_COMPONENT_PACK | \
 			      FSYNC_COMPONENT_PACK_METADATA | \
 			      FSYNC_COMPONENT_COMMIT_GRAPH | \
-			      FSYNC_COMPONENT_INDEX)
+			      FSYNC_COMPONENT_INDEX | \
+			      FSYNC_COMPONENT_REFERENCE)
 
 /*
  * A bitmask indicating which components of the repo should be fsynced.

config.c

@@ -1333,6 +1333,7 @@ static const struct fsync_component_name {
 	{ "commit-graph", FSYNC_COMPONENT_COMMIT_GRAPH },
 	{ "index", FSYNC_COMPONENT_INDEX },
 	{ "objects", FSYNC_COMPONENTS_OBJECTS },
+	{ "reference", FSYNC_COMPONENT_REFERENCE },
 	{ "derived-metadata", FSYNC_COMPONENTS_DERIVED_METADATA },
 	{ "committed", FSYNC_COMPONENTS_COMMITTED },
 	{ "added", FSYNC_COMPONENTS_ADDED },

refs/files-backend.c

@@ -1809,6 +1809,7 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
 	fd = get_lock_file_fd(&lock->lk);
 	if (write_in_full(fd, oid_to_hex(oid), the_hash_algo->hexsz) < 0 ||
 	    write_in_full(fd, &term, 1) < 0 ||
+	    fsync_component(FSYNC_COMPONENT_REFERENCE, get_lock_file_fd(&lock->lk)) < 0 ||
 	    close_ref_gently(lock) < 0) {
 		strbuf_addf(err,
 			    "couldn't write '%s'", get_lock_file_path(&lock->lk));

refs/packed-backend.c

@@ -1262,7 +1262,8 @@ static int write_with_updates(struct packed_ref_store *refs,
 		goto error;
 	}
 
-	if (close_tempfile_gently(refs->tempfile)) {
+	if (fsync_component(FSYNC_COMPONENT_REFERENCE, get_tempfile_fd(refs->tempfile)) ||
+	    close_tempfile_gently(refs->tempfile)) {
 		strbuf_addf(err, "error closing file %s: %s",
 			    get_tempfile_path(refs->tempfile),
 			    strerror(errno));