By default, when you create an `exec.CommandContext` in Go, when the context is cancelled or timed out, Go will SIGKILL the subprocess which does not allow the subprocess to perform any cleanup work. As some git operations in Forgejo will be linked to the current HTTP context, and the current HTTP context will be closed when the HTTP client disconnects, this can theoretically cause SIGKILLs when locks are being held.
This PR contains two fixes:
- Change the behaviour of all subprocesses that Forgejo creates to use a graceful termination, SIGTERM'ing the process, and then SIGKILL'ing it after a timeout.
- Fixes a bug where previously all subprocesses are setup in a process group (by 1d04e8641d), but they were never *killed* in a process group, preventing child processes from receiving these termination signals. Both SIGTERM and SIGKILL are sent to the process group.
Introduces new configuration setting which controls subcommand graceful timeouts. If a subprocess does not shutdown from SIGTERM within `[server].SUBPROCESS_TERMINATE_GRACE` (default 5 seconds), then an error will be logged, and the process will be SIGKILL'd. The error is:
```
2026/07/01 08:31:20 modules/log/init.go:38:func2() [E] Subprocess pid=3790963 (/nix/store/c0277k5giric1mn9dklllavbzvxl6hzb-git-2.53.0/bin/git blame --porcelain 8ee7e7c32b -- options/locale/locale_en-US.ini) failed to terminate from SIGTERM after grace period 0s, and was sent SIGKILL. The subprocess termination may leave incomplete state on the server, such as lock files. `[server].SUBPROCESS_TERMINATE_GRACE` can be changed to give subprocesses more time to cleanly exit.
```
(This was produced on a live server by setting SUBPROCESS_TERMINATE_GRACE to zero seconds, loading a page that does a `git blame`, and hitting escape in the browser quickly.)
### Tests for Go changes
- I added test coverage for Go changes...
- [x] in their respective `*_test.go` for unit tests.
- [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
- [x] `make pr-go` before pushing
### Documentation
- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- Will create a documentation PR with new config settings.
- [ ] I did not document these changes and I do not expect someone else to do it.
### Release notes
- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/13263
Reviewed-by: Andreas Ahlenstorf <aahlenst@noreply.codeberg.org>
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