[PATCH 096/104] start_command: close cmd->err descriptor when fork/spawn fails

[Sam Vilain <sam.vilain@catalyst.net.nz>]

From: bert Dvornik <dvornik+git@gmail.com>

Fix the problem where the cmd->err passed into start_command wasn't
being properly closed when certain types of errors occurr.  (Compare
the affected code with the clean shutdown code later in the function.)

On Windows, this problem would be triggered if mingw_spawnvpe()
failed, which would happen if the command to be executed was malformed
(e.g. a text file that didn't start with a #! line).  If cmd->err was
a pipe, the failure to close it could result in a hang while the other
side was waiting (forever) for either input or pipe close, e.g. while
trying to shove the output into the side band.  On msysGit, this
problem was causing a hang in t5516-fetch-push.

[J6t: With a slight adjustment of the test case, the hang is also
observed on Linux.]

Signed-off-by: bert Dvornik <dvornik+git@gmail.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 run-command.c         |    2 ++
 t/t5516-fetch-push.sh |    2 +-
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/run-command.c b/run-command.c
index eb5c575..c7793f5 100644
--- a/run-command.c
+++ b/run-command.c
@@ -383,6 +383,8 @@ fail_pipe:
 			close(cmd->out);
 		if (need_err)
 			close_pair(fderr);
+		else if (cmd->err)
+			close(cmd->err);
 		errno = failed_errno;
 		return -1;
 	}
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 2de98e6..6a37a4d 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -528,7 +528,7 @@ test_expect_success 'push does not update local refs on failure' '
 	mk_test heads/master &&
 	mk_child child &&
 	mkdir testrepo/.git/hooks &&
-	echo exit 1 >testrepo/.git/hooks/pre-receive &&
+	echo "#!/no/frobnication/today" >testrepo/.git/hooks/pre-receive &&
 	chmod +x testrepo/.git/hooks/pre-receive &&
 	(cd child &&
 		git pull .. master
-- 
1.7.1.rc2.333.gb2668