[PATCH 5/5] transport-helper: fix sync issue on crashes

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Apr 12, 2014, 20:33 UTC
Message-ID: <1397334812-12215-6-git-send-email-felipe.contreras@gmail.com>
In-Reply-To: <1397334812-12215-1-git-send-email-felipe.contreras@gmail.com>

When a remote helper crashes while pushing we should revert back to the state before the push, however, it's possible that `git fast-export` already finished its job, and therefore has exported the marks already.

This creates a synchronization problem because from that moment on `git fast-{import,export}` will have marks that the remote helper is not aware of and all further commands fail (if those marks are referenced).

The fix is to tell `git fast-export` to export to a temporary file, and only after the remote helper has finishes successfully, move to the final destination.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
---
 t/t5801-remote-helpers.sh | 17 ++++++++++++++++-
 transport-helper.c        | 13 +++++++++++--
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/t/t5801-remote-helpers.sh b/t/t5801-remote-helpers.sh
index 613f69a..cf7fd43 100755
--- a/t/t5801-remote-helpers.sh
+++ b/t/t5801-remote-helpers.sh
@@ -207,6 +207,17 @@ test_expect_success 'push update refs failure' '
 	)
 '
 
+clean_mark () {
+	cut -f 2 -d ' ' $1 | git cat-file --batch-check | grep commit | sort > $(basename $1)
+}
+
+cmp_marks () {
+	test_when_finished "rm -rf git.marks testgit.marks" &&
+	clean_mark .git/testgit/$1/git.marks &&
+	clean_mark .git/testgit/$1/testgit.marks &&
+	test_cmp git.marks testgit.marks
+}
+
 test_expect_success 'proper failure checks for fetching' '
 	(GIT_REMOTE_TESTGIT_FAILURE=1 &&
 	export GIT_REMOTE_TESTGIT_FAILURE &&
@@ -221,7 +232,11 @@ test_expect_success 'proper failure checks for pushing' '
 	(GIT_REMOTE_TESTGIT_FAILURE=1 &&
 	export GIT_REMOTE_TESTGIT_FAILURE &&
 	cd local &&
-	test_must_fail git push --all
+	git checkout -b crash master &&
+	echo crash >> file &&
+	git commit -a -m crash &&
+	test_must_fail git push --all &&
+	cmp_marks origin
 	)
 '
 
diff --git a/transport-helper.c b/transport-helper.c
index 2747f98..090c863 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -434,7 +434,7 @@ static int get_exporter(struct transport *transport,
 	fastexport->argv[argc++] = data->signed_tags ?
 		"--signed-tags=verbatim" : "--signed-tags=warn-strip";
 	if (data->export_marks) {
-		strbuf_addf(&tmp, "--export-marks=%s", data->export_marks);
+		strbuf_addf(&tmp, "--export-marks=%s.tmp", data->export_marks);
 		fastexport->argv[argc++] = strbuf_detach(&tmp, NULL);
 	}
 	if (data->import_marks) {
@@ -901,7 +901,16 @@ static int push_refs_with_export(struct transport *transport,
 
 	if (finish_command(&exporter))
 		die("Error while running fast-export");
-	return push_update_refs_status(data, remote_refs);
+	if (push_update_refs_status(data, remote_refs))
+		return 1;
+
+	if (data->export_marks) {
+		strbuf_addf(&buf, "%s.tmp", data->export_marks);
+		rename(buf.buf, data->export_marks);
+		strbuf_release(&buf);
+	}
+
+	return 0;
 }
 
 static int push_refs(struct transport *transport,

-- 
1.9.1+fc3.9.gc73078e