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SZEDER reported that t5411 failed in Travis CI's s390x environment a
couple of times, and could be reproduced with '--stress' test on this
specific environment. The test failure messages might look like this:
+ test_cmp expect actual
--- expect 2021-01-17 21:55:23.430750004 +0000
+++ actual 2021-01-17 21:55:23.430750004 +0000
@@ -1 +1 @@
-<COMMIT-A> refs/heads/main
+<COMMIT-A> refs/heads/maifatal: the remote end hung up unexpectedly
error: last command exited with $?=1
not ok 86 - proc-receive: not support push options (builtin protocol)
The file 'actual' is filtered from the file 'out' which contains result
of 'git show-ref' command. Due to the error messages from other process
is written into the file 'out' accidentally, t5411 failed. SZEDER finds
the root cause of this issue:
- 'git push' is executed with its standard output and error redirected
to the file 'out'.
- 'git push' executes 'git receive-pack' internally, which inherits
the open file descriptors, so its output and error goes into that
same 'out' file.
- 'git push' ends without waiting for the close of 'git-receive-pack'
for some cases, and the file 'out' is reused for test of
'git show-ref' afterwards.
- A mixture of the output of 'git show-ref' abd 'git receive-pack'
leads to this issue.
The first intuitive reaction to resolve this issue is to remove the
file 'out' after use, so that the newly created file 'out' will have a
different file descriptor and will not be overwritten by the
'git receive-pack' process. But Johannes pointed out that removing an
open file is not possible on Windows. So we use different temporary
file names to store the output of 'git push' to solve this issue.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Johannes Sixt <j6t@kdbg.org>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Git calls an internal `execute_commands` function to handle commands
sent from client to `git-receive-pack`. Regardless of what references
the user pushes, git creates or updates the corresponding references if
the user has write-permission. A contributor who has no
write-permission, cannot push to the repository directly. So, the
contributor has to write commits to an alternate location, and sends
pull request by emails or by other ways. We call this workflow as a
distributed workflow.
It would be more convenient to work in a centralized workflow like what
Gerrit provided for some cases. For example, a read-only user who
cannot push to a branch directly can run the following `git push`
command to push commits to a pseudo reference (has a prefix "refs/for/",
not "refs/heads/") to create a code review.
git push origin \
HEAD:refs/for/<branch-name>/<session>
The `<branch-name>` in the above example can be as simple as "master",
or a more complicated branch name like "foo/bar". The `<session>` in
the above example command can be the local branch name of the client
side, such as "my/topic".
We cannot implement a centralized workflow elegantly by using
"pre-receive" + "post-receive", because Git will call the internal
function "execute_commands" to create references (even the special
pseudo reference) between these two hooks. Even though we can delete
the temporarily created pseudo reference via the "post-receive" hook,
having a temporary reference is not safe for concurrent pushes.
So, add a filter and a new handler to support this kind of workflow.
The filter will check the prefix of the reference name, and if the
command has a special reference name, the filter will turn a specific
field (`run_proc_receive`) on for the command. Commands with this filed
turned on will be executed by a new handler (a hook named
"proc-receive") instead of the internal `execute_commands` function.
We can use this "proc-receive" command to create pull requests or send
emails for code review.
Suggested by Junio, this "proc-receive" hook reads the commands,
push-options (optional), and send result using a protocol in pkt-line
format. In the following example, the letter "S" stands for
"receive-pack" and letter "H" stands for the hook.
# Version and features negotiation.
S: PKT-LINE(version=1\0push-options atomic...)
S: flush-pkt
H: PKT-LINE(version=1\0push-options...)
H: flush-pkt
# Send commands from server to the hook.
S: PKT-LINE(<old-oid> <new-oid> <ref>)
S: ... ...
S: flush-pkt
# Send push-options only if the 'push-options' feature is enabled.
S: PKT-LINE(push-option)
S: ... ...
S: flush-pkt
# Receive result from the hook.
# OK, run this command successfully.
H: PKT-LINE(ok <ref>)
# NO, I reject it.
H: PKT-LINE(ng <ref> <reason>)
# Fall through, let 'receive-pack' to execute it.
H: PKT-LINE(ok <ref>)
H: PKT-LINE(option fall-through)
# OK, but has an alternate reference. The alternate reference name
# and other status can be given in options
H: PKT-LINE(ok <ref>)
H: PKT-LINE(option refname <refname>)
H: PKT-LINE(option old-oid <old-oid>)
H: PKT-LINE(option new-oid <new-oid>)
H: PKT-LINE(option forced-update)
H: ... ...
H: flush-pkt
After receiving a command, the hook will execute the command, and may
create/update different reference. For example, a command for a pseudo
reference "refs/for/master/topic" may create/update different reference
such as "refs/pull/123/head". The alternate reference name and other
status are given in option lines.
The list of commands returned from "proc-receive" will replace the
relevant commands that are sent from user to "receive-pack", and
"receive-pack" will continue to run the "execute_commands" function and
other routines. Finally, the result of the execution of these commands
will be reported to end user.
The reporting function from "receive-pack" to "send-pack" will be
extended in latter commit just like what the "proc-receive" hook reports
to "receive-pack".
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Jiang Xin
Johannes Schindelin