[PATCH] Make git-send-pack exit with error when some refs couldn't be pushed out

[PATCH] Make git-send-pack exit with error when some refs couldn't be pushed out

[Petr Baudis]

In case some refs couldn't be pushed out due to an error (mostly the
not-a-proper-subset error), make git-send-pack exit with non-zero status
after the push is over (that is, it still tries to push out the rest
of the refs).

Cogito (0.17pre only, 0.16 is unaffected) needs to know that the push
failed so that it won't update its remote branch head pointer - otherwise
it gets out of sync, which can lead even to loss of commits on the local
side (this happenned to Jonas Fonseca - thanks for the report, BTW).
I sort of expected that git-send-pack would return an error in case
of a failure, so just applying this should magically fix Cogito.

I don't insist on this particular solution though - a fetch-pack-alike
approach where I get the list of changed refs on stdout is fine too
(currently I get something on stderr, but I'm reluctant to grab stderr
of GIT commands and try to heuristically mangle it).

At any rate, please consider this a major problem from Cogito perspective.

Signed-off-by: Petr Baudis <pasky@suse.cz>
---

 send-pack.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/send-pack.c b/send-pack.c
index f61c15c..6ce0d9f 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -179,6 +179,7 @@ static int send_pack(int in, int out, in
 {
 	struct ref *ref;
 	int new_refs;
+	int ret = 0;
 
 	/* No funny business with the matcher */
 	remote_tail = get_remote_heads(in, &remote_refs, 0, NULL, 1);
@@ -232,6 +233,7 @@ static int send_pack(int in, int out, in
 				error("remote '%s' object %s does not "
 				      "exist on local",
 				      ref->name, sha1_to_hex(ref->old_sha1));
+				ret = -2;
 				continue;
 			}
 
@@ -245,12 +247,14 @@ static int send_pack(int in, int out, in
 				error("remote ref '%s' is not a strict "
 				      "subset of local ref '%s'.", ref->name,
 				      ref->peer_ref->name);
+				ret = -2;
 				continue;
 			}
 		}
 		memcpy(ref->new_sha1, ref->peer_ref->new_sha1, 20);
 		if (is_zero_sha1(ref->new_sha1)) {
 			error("cannot happen anymore");
+			ret = -3;
 			continue;
 		}
 		new_refs++;
@@ -267,7 +271,7 @@ static int send_pack(int in, int out, in
 	if (new_refs)
 		pack_objects(out, remote_refs);
 	close(out);
-	return 0;
+	return ret;
 }
 
 

Re: [PATCH] Make git-send-pack exit with error when some refs couldn't be pushed out

[Junio C Hamano]

Petr Baudis <pasky@suse.cz> writes:

> In case some refs couldn't be pushed out due to an error (mostly the
> not-a-proper-subset error), make git-send-pack exit with non-zero status
> after the push is over (that is, it still tries to push out the rest
> of the refs).

I agree this change to send-pack is a good fix (I haven't looked
at the code, but the above description describes a good fix).

However, I am not quite sure if the recent change to Cogito to
update the mirror of remote branch is a good one.  Since I am
not a Cogito user, I did not question it when I saw the change,
but I wondered what you are using the cached "remote ref is
supposed to be pointing at this commit" knowledge for.  If it is
only "pretending to have fetched the remote branch immediately
after we pushed into it before anybody else touched the same
remote branch", then it probably is benign.  But this bit
puzzles and worries me:

> ... otherwise
> it gets out of sync, which can lead even to loss of commits on the local
> side (this happenned to Jonas Fonseca - thanks for the report, BTW).

I do not remember seeing that report so I do not know how that
lossage happens with unreleased Cogito, but I suspect there is
something very fishy going on here.  I presume it happens when
the next fetch/pull from the remote is run, but if the locally
cached information can affect the next fetch/pull in such a way,
wouldn't updates by other people to the shared remote repository
branch also cause things to go out-of-sync and cause the same
breakage?

Re: [PATCH] Make git-send-pack exit with error when some refs couldn't be pushed out

[Petr Baudis]

Dear diary, on Wed, Dec 14, 2005 at 02:50:02AM CET, I got a letter
where Junio C Hamano <junkio@cox.net> said that...
> However, I am not quite sure if the recent change to Cogito to
> update the mirror of remote branch is a good one.  Since I am
> not a Cogito user, I did not question it when I saw the change,
> but I wondered what you are using the cached "remote ref is
> supposed to be pointing at this commit" knowledge for.  If it is
> only "pretending to have fetched the remote branch immediately
> after we pushed into it before anybody else touched the same
> remote branch", then it probably is benign.

Exactly, we're just pretending that. It's useful since cg-fetch's
diff-tree output is less confusing then, cg-log -r <remotebranch> and
cg-diff -r ... gives expected results, etc.

> But this bit puzzles and worries me:
> 
> > ... otherwise
> > it gets out of sync, which can lead even to loss of commits on the local
> > side (this happenned to Jonas Fonseca - thanks for the report, BTW).
> 
> I do not remember seeing that report so I do not know how that
> lossage happens with unreleased Cogito, but I suspect there is
> something very fishy going on here.  I presume it happens when
> the next fetch/pull from the remote is run, but if the locally
> cached information can affect the next fetch/pull in such a way,
> wouldn't updates by other people to the shared remote repository
> branch also cause things to go out-of-sync and cause the same
> breakage?

Jonas only reported it on IRC as weird cg-commit behaviour (which it
appeared to be, but the cause turned out to be this and the nice
side-effect that this kind of breakage cannot lose you actual data at
least, just metadata).

If the push really happened, this shouldn't be a problem, since then we
get into a "fast-forward relation" to the remote branch, and commits by
other people don't affect it either, since they don't break this
relation. The "interesting behaviour" Cogito implements happens only if
your current HEAD == <the_old_remote_head>, which can't happen when
other people commit, only when you push it out to the remote head.

What kicks in is the fast-forward behaviour change I proposed quite some
time ago on the mailing list and got zero feedback about --- when
updating from a remote branch, the Cogito 0.17pre's fast-forward test
is extended from

	if (head ancestor_of remote_new)

to

	if (head ancestor_of remote_new OR head == remote_old)

which will make fast-forward able to follow even remote rebases
and should have no negative side-effects as long as remote_old
was correct (which it is except when our bug comes out). So in
the reported case, remote_old was set to head, while remote_new
stayed as before, and Cogito therefore thought that the remote
branch just got rebased from head to remote_new, and adjusted
the head appropriately.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
VI has two modes: the one in which it beeps and the one in which
it doesn't.

Re: [PATCH] Make git-send-pack exit with error when some refs cou ldn't be pushed out

[Jon Loeliger]

On Tue, 2005-12-13 at 20:30, Petr Baudis wrote:

> 
> Jonas only reported it on IRC as weird cg-commit behaviour (which it

Gah.  Are we IRCing now too these days?  Did I miss a step
or an announcment?  I thought we were all doing a reasonably
good job of communicating here on list...  And if I do need
to sit-n-watch some IRC channel somewhere to get a complete
git-fix, please let me know what it is! :-)

Thanks,
jdl

Re: [PATCH] Make git-send-pack exit with error when some refs cou ldn't be pushed out

[Petr Baudis]

Dear diary, on Wed, Dec 14, 2005 at 05:15:09PM CET, I got a letter
where Jon Loeliger <jdl@freescale.com> said that...
> On Tue, 2005-12-13 at 20:30, Petr Baudis wrote:
> > Jonas only reported it on IRC as weird cg-commit behaviour (which it
> 
> Gah.  Are we IRCing now too these days?  Did I miss a step
> or an announcment?

I mentioned the #git channel on the FreeNode network in several Cogito
announcements, but this problem report was actually in a different
channel (#elinks, since it occurred during work on ELinks) and it
wouldn't make a difference if it was on a query or in a private mail.

> I thought we were all doing a reasonably good job of communicating
> here on list...

Sure, all important things are going on here, but it's often much more
convenient to do some troubleshooting and stuff over IRC, and way too
many people also mail me privately (sometimes it makes sense, sometimes
they would be better off cc'ing the list).

#git serves mainly as quick help wrt. GIT usage, sometimes people report
problems there (but for non-Cogito problems, I usually redir them to the
mailing list), and sometimes (but quite rarely) larger feature-wise
discussion spins out; but if it's about to get anything near real, it
usually hits the mailing list anyway. Oh, and CIA reports Cogito commits
on the channel.

The only IRC-only effort ever (so far) was I believe adding the
cg-switch command.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
VI has two modes: the one in which it beeps and the one in which
it doesn't.