tests: disable fsync everywhere

The "GIT_TEST_FSYNC" environment variable now exists for
disabling fsync() even on packfiles and other "critical" data.

Running "make test -j8 NO_SVN_TESTS=1" on a noisy 8-core system
on an HDD, test runtime drops from ~4 minutes down to ~3 minutes.
Using "GIT_TEST_FSYNC=1" re-enables fsync() for comparison
purposes.

SVN interopability tests are minimally affected since SVN will
still use fsync in various places.

This will also be useful for 3rd-party tools which create
throwaway git repositories of temporary data, but remains
undocumented for end users.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/write-or-die.c b/write-or-die.c
index d33e68f6ab..4e48194676 100644
--- a/write-or-die.c
+++ b/write-or-die.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "config.h"
 #include "run-command.h"
 
 /*
@@ -57,6 +58,10 @@ void fprintf_or_die(FILE *f, const char *fmt, ...)
 
 void fsync_or_die(int fd, const char *msg)
 {
+	if (use_fsync < 0)
+		use_fsync = git_env_bool("GIT_TEST_FSYNC", 1);
+	if (!use_fsync)
+		return;
 	while (fsync(fd) < 0) {
 		if (errno != EINTR)
 			die_errno("fsync error on '%s'", msg);