upload-pack: Use finish_{command,async}() instead of waitpid().

upload-pack spawns two processes, rev-list and pack-objects, and carefully
monitors their status so that it can report failure to the remote end.
This change removes the complicated procedures on the grounds of the
following observations:

- If everything is OK, rev-list closes its output pipe end, upon which
  pack-objects (which reads from the pipe) sees EOF and terminates itself,
  closing its output (and error) pipes. upload-pack reads from both until
  it sees EOF in both. It collects the exit codes of the child processes
  (which indicate success) and terminates successfully.

- If rev-list sees an error, it closes its output and terminates with
  failure. pack-objects sees EOF in its input and terminates successfully.
  Again upload-pack reads its inputs until EOF. When it now collects
  the exit codes of its child processes, it notices the failure of rev-list
  and signals failure to the remote end.

- If pack-objects sees an error, it terminates with failure. Since this
  breaks the pipe to rev-list, rev-list is killed with SIGPIPE.
  upload-pack reads its input until EOF, then collects the exit codes of
  the child processes, notices their failures, and signals failure to the
  remote end.

- If upload-pack itself dies unexpectedly, pack-objects is killed with
  SIGPIPE, and subsequently also rev-list.

The upshot of this is that precise monitoring of child processes is not
required because both terminate if either one of them dies unexpectedly.
This allows us to use finish_command() and finish_async() instead of
an explicit waitpid(2) call.

The change is smaller than it looks because most of it only reduces the
indentation of a large part of the inner loop.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/t/t5530-upload-pack-error.sh b/t/t5530-upload-pack-error.sh
new file mode 100755
index 0000000000..cc8949e3ef
--- /dev/null
+++ b/t/t5530-upload-pack-error.sh
@@ -0,0 +1,75 @@
+#!/bin/sh
+
+test_description='errors in upload-pack'
+
+. ./test-lib.sh
+
+D=`pwd`
+
+corrupt_repo () {
+	object_sha1=$(git rev-parse "$1") &&
+	ob=$(expr "$object_sha1" : "\(..\)") &&
+	ject=$(expr "$object_sha1" : "..\(..*\)") &&
+	rm -f ".git/objects/$ob/$ject"
+}
+
+test_expect_success 'setup and corrupt repository' '
+
+	echo file >file &&
+	git add file &&
+	git rev-parse :file &&
+	git commit -a -m original &&
+	test_tick &&
+	echo changed >file &&
+	git commit -a -m changed &&
+	corrupt_repo HEAD:file
+
+'
+
+test_expect_failure 'fsck fails' '
+
+	git fsck
+'
+
+test_expect_success 'upload-pack fails due to error in pack-objects' '
+
+	! echo "0032want $(git rev-parse HEAD)
+00000009done
+0000" | git-upload-pack . > /dev/null 2> output.err &&
+	grep "pack-objects died" output.err
+'
+
+test_expect_success 'corrupt repo differently' '
+
+	git hash-object -w file &&
+	corrupt_repo HEAD^^{tree}
+
+'
+
+test_expect_failure 'fsck fails' '
+
+	git fsck
+'
+test_expect_success 'upload-pack fails due to error in rev-list' '
+
+	! echo "0032want $(git rev-parse HEAD)
+00000009done
+0000" | git-upload-pack . > /dev/null 2> output.err &&
+	grep "waitpid (async) failed" output.err
+'
+
+test_expect_success 'create empty repository' '
+
+	mkdir foo &&
+	cd foo &&
+	git init
+
+'
+
+test_expect_failure 'fetch fails' '
+
+	git fetch .. master
+
+'
+
+test_done