[PATCH 5/5] refs.c: write values to lock files early for committing

[Stefan Beller <sbeller@google.com>]

By writing the values to the lock file early we have a better sequence
of system calls. Before this commit we had

    open(), close(), open(), fdopen(), write(), fclose(), rename()

Now there is:

    open(), fdopen(), write(), fclose(), rename()

The first four operations are performed in the first loop of
ref_transaction_commit ("/* Acquire all locks while verifying
old values */"), while the renameing is left to the next loop.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 refs.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/refs.c b/refs.c
index c108c95..3d1890f 100644
--- a/refs.c
+++ b/refs.c
@@ -3767,6 +3767,15 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 				    update->refname);
 			goto cleanup;
 		}
+		if (!is_null_sha1(update->new_sha1)) {
+			if (write_ref_sha1(update->lock, update->new_sha1,
+					   update->msg)) {
+				strbuf_addf(err, "Cannot update the ref '%s'.",
+					    update->refname);
+				ret = TRANSACTION_GENERIC_ERROR;
+				goto cleanup;
+			}
+		}
 		/* Do not keep all lock files open at the same time. */
 		close_ref(update->lock);
 	}
@@ -3776,9 +3785,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		struct ref_update *update = updates[i];
 
 		if (!is_null_sha1(update->new_sha1)) {
-			if (write_ref_sha1(update->lock, update->new_sha1,
-					   update->msg)
-			    || commit_ref(update->lock, update->new_sha1)) {
+			if (commit_ref(update->lock, update->new_sha1)) {
 				strbuf_addf(err, "Cannot update the ref '%s'.",
 					    update->refname);
 				ret = TRANSACTION_GENERIC_ERROR;
-- 
2.2.1.62.g3f15098