doc: use an absolute path in sys.path to work around a python DLL loading bug This bug[1] was causing the zstd entry under "Available Compression Engines" to be omitted from the documentation for some versions of python3. I could upgrade, but past upgrades have broken venvs and clobbered installed packages. It's a trivial workaround, so there's no sense in leaving this subtle issue. It was flushed out by changing the module policy here from 'allow' to 'c', and seeing this error: ImportError: DLL load failed while importing parsers: The parameter is incorrect. [1] https://github.com/python/cpython/issues/87271 Differential Revision: https://phab.mercurial-scm.org/D12599

rhg: fix dirstate-v2 data file removal system In D12581 I introduced logic to remove the previous dirstate-v2 data file after a new one is created (and its corresponding docket), but the logic was flawed. I fixed it and made it simpler to understand by gather all logic in a single expression. Differential Revision: https://phab.mercurial-scm.org/D12586

rhg: use `Command::exec` instead of `Command::status` `rhg` is supposed to be a transparent executable, using a subprocess defeats that purpose. See inline comments for more details. This also introduces the `which` crate to check if the fallback executable actually exists to help debugging (plain `execve` doesn't give much information). The error code 253 is used to signify that the fallback is not found, but may mean in the future that it is otherwise invalid if we start being more specific. Differential Revision: https://phab.mercurial-scm.org/D12578

commit: don't use hard-coded `.hg/last-message.txt` path in error message Whoever wrote D8463 just used a hard-coded path to `.hg/last-message.text` instead of using the relative path that was already available in the `msgfn` variable (and used just a few lines up in related message). Let's fix that. Differential Revision: https://phab.mercurial-scm.org/D12585

rust-dirstate-v2: clean up previous data file after the docket is written This was overlooked before and caused many data files to keep living forever. We could potentially consider adding a random cleanup of them in case they slipped through one day. Differential Revision: https://phab.mercurial-scm.org/D12581

rust-dirstate-v2: save proper data size if no new data on append This is currently only triggered with the tests ran with `--rhg` without `--rust`, by "luck", there probably always was something to write, like an mtime when also using Rust extensions alongside `rhg`. Differential Revision: https://phab.mercurial-scm.org/D12580

procutil: avoid `+= None` when writing to full std{err,out} descriptor on py3 The write function returns `None` if there was no room to write the given data[1]. I don't like that this is effectively an infinite loop if there's never any progress emptying the underlying buffer, but we're no worse off than before, and it fixes random stacktrace popups seen in the py3 build of TortoiseHg. [1] https://docs.python.org/3/library/io.html#io.RawIOBase.write Differential Revision: https://phab.mercurial-scm.org/D12555