Unstaged changes can be useful or necessary for some tasks
e.g. absolute emergency (where even faking the state of a staging is
not really desirable, if that's even possible anymore), or changes
which are so broad they're difficult to stage (e.g. t10s updates).
Add a new object which serves as a queue for patch to direct-apply,
with support for either text patches (udiff style out of git show or
format-patch) or commits to cherry-pick. In the former case, the part
of the show / format-patch before the diff itself is used for the
commit metadata (author, committer, dates, message) whereas for the
commit version the commit itself is reused as-is.
Applied patches are simply disabled for traceability.
Fixes#926
Given branch A, and branch B forked from it. If B removes a file which
a PR to A later modifies, on forward port Git generates a
modify/delete conflict (as in one side modifies a file which the
other deleted).
So far so good, except while it does notify the caller of the issue
the modified file is just dumped as-is into the working copy (or
commit), which essentially resurrects it.
This is an issue, *especially* as the file is already part of a
commit (rather tan just a U local file), if the developer fixes the
conflict "in place" rather than re-doing the forward-port from scratch
it's easy to miss the reincarnated file (and possibly the changes that
were part of it too), which at best leaves parasitic dead code in the
working copy. There is also no easy way for the runbot to check it as
adding unimported standalone files while rare is not unknown
e.g. utility scripts (to say nothing of JS where we can't really track
the usages / imports at all).
To resolve this issue, during conflict generation post-process
modify/delete to insert artificial conflict markers, the file should
be syntactically invalid so linters / checkers should complain, and
the minimal check has a step looking for conflict markers which should
fire and prevent merging the PR.
Fixes#896
The goal is to reduce maintenance and odd disk interactions &
concurrency issues, by not creating concurrent clones, not having to
push forks back in the repository, etc... it also removes the need to
cleanup "scratch" working copies though that looks not to have been an
issue in a while.
The work is done on isolated objects without using or mutating refs,
so even concurrent work should not be a problem.
This turns out to not be any more verbose (less so if anything) than
using `cherry-pick`, as that is not really designed for scripted /
non-interactive use, or for squashing commits thereafter. Working
directly with trees and commits is quite a bit cleaner even without a
ton of helpers.
Much of the credit goes to Julia Evans for [their investigation of
3-way merges as the underpinnings of cherry-picking][3-way merge],
this would have been a lot more difficult if I'd had to rediscover the
merge-base trick independently.
A few things have been changed by this:
- The old trace/stderr from cherrypick has disappeared as it's
generated by cherrypick, but for a non-interactive use it's kinda
useless anyway so I probably should have looked into removing it
earlier (I think the main use was investigation of the inflateinit
issue).
- Error on emptied commits has to be hand-rolled as `merge-tree`
couldn't care less, this is not hard but is a bit annoying.
- `merge-tree`'s conflict information only references raw commits,
which makes sense, but requires updating a bunch of tests. Then
again so does the fact that it *usually* doesn't send anything to
stderr, so that's usually disappearing.
Conveniently `merge-tree` merges the conflict marker directly in the
files / tree so we don't have to mess about moving them back out of
the repository and into the working copy as I assume cherry-pick does,
which means we don't have to try and commit them back in ether. That
is a huge part of the gain over faffing about with the working copy.
Fixes#847
[3-way merge]: https://jvns.ca/blog/2023/11/10/how-cherry-pick-and-revert-work/
Automating via parameters is riskier as we can hit the CLI
limitations (cf 0a839a4857). Going
through stdin is a lot safer and cleaner when automating, and it's not
much of an imposition here.
Before this, we would check if a repository had a name and run
maintenance on it, leading to repeated (but unnoticed until now
because I didn't monitor it) tracebacks as the maintenance cron would
fail to find the local repo then run maintenance on nowhere anyway.
Also augment the repo-finding process to try and get better
information about what it's doing when it fails, rather than failing
completely silently.
Turns out I've always been mistaken about the handling of quotes
*inside* shell parameters, apparently they are always consumed by the
shell unless nested so
--foo="bar"
reaches the underlying program as
--foo=bar
This means when using subprocess (without shell=True), adding the
quotes leads to mishandling of the parameters (as the subprocess now
has quotes it's not equipped to deal with).
This exact error is made in the `--pretty` parameter of git show,
locally this results in the author name and the committer email being
terminated by double quotes although somehow other layers seem to
exclude those from the end result (I assume `commit-tree` strips the
quotes from the envvars under the assumption that users can mistakenly
quote them or something?
Anyway while it does not seem harmful (so far), better safe than
sorry.
The logging line was copied over from the github-api version, but it
was not correctly fixed up to match, leading to a lot of spam on
stderr when debug is enabled (aka spams journalctl on the production
server).
Splat the logging call out of `rebase` and into the various callers,
so they have access to the pr object to log it.
The low-level APIs used by the staging process don't do any merge
check, so because of the way Git works it's possible for them to merge
commits with content as empty commits, e.g. if something was merged
then backported and the backport was merged on top. This should
trigger a merge failure as we don't really want to merge newly
empty. This is a feature which some high level commands of git
support, kind-of, e.g. by default `git rebase --interactive` will ask
about newly empty commits.
Take care to allow merging already-empty commits, as these do have a
use for signaling, freezes, ....
Fixes#809
It has been a consideration for a while, but the pain of subtly
interacting with git via the ignominous CLI kept it back. Then ~~the
fire nation attacked~~ github got more and more tight-fisted (and in
some ways less reliable) with their API.
Staging pretty much just interacts with the git database, so it's both
a facultative github operator (it can just interact with git directly)
and a big consumer of API requests (because the git database endpoints
are very low level so it takes quite a bit of work to do anything
especially when high-level operations like rebase have to be
replicated by hand).
Furthermore, an issue has also been noticed which can be attributed to
using the github API (and that API's reliability getting worse): in
some cases github will fail to propagate a ref update / reset, so when
staging 2 PRs it's possible that the second one is merged on top of
the temporary branch of the first one, yielding a kinda broken commit
(in that it's a merge commit with a broken error message) instead of
the rebase / squash commit we expected.
As it turns out it's a very old issue but only happened very early so
was misattributed and not (sufficiently) guarded against:
- 41bd82244bb976bbd4d4be5e7bd792417c7dae6b (October 8th 2018) was
spotted but thought to be a mergebot issue (might have been one of
the opportunities where ref-checks were added though I can't find
any reference to the commit in the runbot repo).
- 2be25052e147b151d1d8a5bc73cceb351586ce03 (October 15th, 2019) was
missed (or ignored).
- 5a9fe7a7d05a9df7186072a7bffd60c6b428fd0e (July 31st, 2023) was
spotted, but happened at a moment where everything kinda broke
because of github rate-limiting ref updates, so the forensics were
difficult and it was attributed to rate limiting issues.
- f10d03bf0f2e8f88f62a5d8356b84f714196130f (August 24th, 2023) broke
the camel's back (and the head block): the logs were not too
interspersed with other garbage and pretty clear that github ack'd a
ref update, returned the correct oid when checking the ref, then
returned the wrong oid when fetching it later on.
No Working Copy
===============
The working copy turns out to not be necessary, the plumbing commands
we *need* work just fine on a bare repository.
Working without a WC means we had to reimplement the high level
operations (rebase) by hand much as we'd done previously, *but* we
needed to do that anyway as git doesn't seem to provide any way to
retrieve the mapping when rebasing/cherrypicking, and cherrypicking by
commit doesn't work well as it can't really find the *merge base* it
needs.
Forward-porting can almost certainly be implemented similarly (with
some overhead), issue #803 has been opened to keep track of the idea.
No TMP
======
The `tmp.` branches are no more, the process of creating stagings is
based entirely around oids, if staging something fails we can just
abandon the oids (they'll be collected by the weekly GC), we only
need to update the staging branches at the very end of the process.
This simplifies things a fair bit.
For now we have stopped checking for visibility / backoff as we're
pushing via git, hopefully it is a more reliable reference than the
API.
Commmit Message Formatting
==========================
There's some unfortunate churn in the test, as the handling of
trailing newlines differs between github's APIs and git itself.
Fixes#247
PS: It might be a good idea to use pygit2 instead of the CLI
eventually, the library is typed which is nice, and it avoids
shelling out although that's really unlikely to be a major cost.
If the stagings are going to be created locally (via a git working
copy rather than the github API), the mergebot part needs to have
access to the cache, so move the cache over. Also move the maintenance
cron.
In an extermely minor way, this prefigures the (hopeful) eventual
merging of the ~~planes~~ modules.
