|
In the GitHub workflow used in Git's CI builds, the `vs test` jobs use a
subset of a specific revision of Git for Windows' SDK to run Git's test
suite. This revision is validated by another CI workflow to ensure that
said revision _can_ run Git's test suite successfully, skipping buggy
updates in Git for Windows' SDK.
The `win+Meson test` jobs do things differently, quite differently. They
use the Bash of the Git for Windows version that is installed on the
runners to run Git's test suite.
This difference has consequences.
When 68cb0b5253a0 (builtin/receive-pack: add option to skip connectivity
check, 2025-05-20) introduced a test case that uses `tee <file> | git
receive-pack` as `--receive-pack` parameter (imitating an existing
pattern in the same test script), it hit just the sweet spot to trigger
a bug in the MSYS2 runtime shipped in Git for Windows v2.49.0. This
version is the one currently installed on GitHub's runners.
The problem is that the `git receive-pack` process finishes while the
`tee` process does not need to write anything anymore and therefore does
not receive an EOF. Instead, it should receive a SIGPIPE, but the bug in
the MSYS2 runtime prevents that from working as intended. As a
consequence, the `tee` process waits for more input from the `git.exe
send-pack` process but none is coming, and the test script patiently
waits until the 6h timeout hits.
Only every once in a while, the `git receive-pack` process manages to
send an EOF to the `tee` process and no hang occurs. Therefore, the
problem can be worked around by cancelling the clearly-hanging job after
twenty or so minutes and re-running it, repeating the process about half
a dozen times, until the hang was successfully avoided.
This bug in the MSYS2 runtime has been fixed in the meantime, which is
the reason why the same test case causes no problems in the `win test`
and the `vs test` jobs.
This will continue to be the case until the Git for Windows version on
the GitHub runners is upgraded to a version that distributes a newer
MSYS2 runtime version. However, as of time of writing, this _is_ the
latest Git for Windows version, and will be for another 1.5 weeks, until
Git v2.50.0 is scheduled to appear (and shortly thereafter Git for
Windows v2.50.0). Traditionally it takes a while before the runners pick
up the new version.
We could just wait it out, six hours at a time.
Here, I opt for an alternative: Detect the buggy MSYS2 runtime and
simply skip the test case. It's not like the `receive-pack` test cases
are specific to Windows, and even then, to my chagrin the CI runs in
git-for-windows/git spend around ten hours of compute time each and
every time to run the entire test suite on all the platforms, even the
tests that cover cross-platform code, and for Windows alone we do that
three times: with GCC, with MSVC, and with MSVC via Meson. Therefore, I
deem it more than acceptable to skip this test case in one of those
matrices.
For good luck, also the preceding test case is skipped in that scenario,
as it uses the same `--receive-pack=tee <file> | git receive-pack`
pattern, even though I never observed that test case to hang in
practice.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
During git-receive-pack(1), connectivity of the object graph is
validated to ensure that the received packfile does not leave the
repository in a broken state. This is done via git-rev-list(1) and
walking the objects, which can be expensive for large repositories.
Generally, this check is critical to avoid an incomplete received
packfile from corrupting a repository. Server operators may have
additional knowledge though around exactly how Git is being used on the
server-side which can be used to facilitate more efficient connectivity
computation of incoming objects.
For example, if it can be ensured that all objects in a repository are
connected and do not depend on any missing objects, the connectivity of
newly written objects can be checked by walking the object graph
containing only the new objects from the updated tips and identifying
the missing objects which represent the boundary between the new objects
and the repository. These boundary objects can be checked in the
canonical repository to ensure the new objects connect as expected and
thus avoid walking the rest of the object graph.
Git itself cannot make the guarantees required for such an optimization
as it is possible for a repository to contain an unreachable object that
references a missing object without the repository being considered
corrupt.
Introduce the --skip-connectivity-check option for git-receive-pack(1)
which bypasses this connectivity check to give more control to the
server-side. Note that without proper server-side validation of newly
received objects handled outside of Git, usage of this option risks
corrupting a repository.
Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
