repair: improve performance of detection of revisions affected by issue6528 Explanations inside the patch. I've tested this on Mozilla-Central and it's 5 times faster than the naive approach on my laptop. Differential Revision: https://phab.mercurial-scm.org/D11262

debugcommands: introduce a debug command to repair repos affected by issue6528 This command is quite basic and slow, it will loop over the entirety of the filelogs in the repository and check each revision for corruption, then fixes the affected filelogs. It takes under 25 minutes for Mozilla-Central on my not-top-of-the-line laptop, using the `--to-report` and `--from-report` options will make this pretty tolerable to use, I think. This change also introduces a test for the fix. Differential Revision: https://phab.mercurial-scm.org/D11239

contrib: switch the Windows bootstrap environment to py3.9 Use the built in `venv` module instead of `virtualenv` for simplicity, and upgrade to a modern Mercurial that supports py3. One issue here is that `venv` doesn't copy `python3{,Y}.dll` into the `Scripts` subdirectory, so running the `hg.exe` that gets installed immediately fails on a clean system because Python isn't in `PATH`. There is code in `python.exe` to detect when it is in a venv and add the original python install to the DLL lookup path, which we don't do in `hg.exe` yet. The simple workaround for now is to run the `hg` script with `python.exe`. Typically `PYTHONLEGACYWINDOWSSTDIO` must be set in the environment on Windows, but the clone process works without it. Differential Revision: https://phab.mercurial-scm.org/D11275

contrib: comment out the 64-bit py38 dependency installation on Windows Not sure what is going on here, but it appears to not install py3.8 x64 in the usual `C:\hgdev` directory. The x32 installer works fine. I'm assuming this is a bug in this version of the installer, but didn't look into it too much. Differential Revision: https://phab.mercurial-scm.org/D11274

contrib: drop python2.7 from the Windows dependency install script While we aren't quite ready to drop py27 yet, the MS compiler is no longer available from MS (there is a copy on github if it's really needed), and that causes the script to fail. Differential Revision: https://phab.mercurial-scm.org/D11273

contrib: log the command and args for every process installing windows deps This is a little noisier, but makes it simple to debug when things fail. Differential Revision: https://phab.mercurial-scm.org/D11272

windows-ci: run Windows CI automatically alongside the others This will enable us to make Windows Python 3 a first-class citizen for the next 6.0 cycle. We will probably get some flaky tests and we're missing others that are skipped, but we'll turn them on it future patches. Differential Revision: https://phab.mercurial-scm.org/D11256

vfs: always use / as file separator (issue6546) Various part of vfs already enforce `/` usage and using `\` confuse the encoded vfs. So we simply use `/` all the time. Differential Revision: https://phab.mercurial-scm.org/D11260

subrepo: compare normalised vfs path Otherwise the realpath call can turn `/` into `\` on windows confusing the check. (We probably needs this in more location) Differential Revision: https://phab.mercurial-scm.org/D11259

pager: account for flakiness in Windows output This test case is cursed and probably not worth losing more time over. This makes apparent what the intended behavior is while still removing the flakiness from the CI. Differential Revision: https://phab.mercurial-scm.org/D11257

windows-ci: clean up the Heptapod CI file now that the baseline is solid Enough work has been done one the CI side, this now works with little effort on our side. The next patch will remove the manual switch. Differential Revision: https://phab.mercurial-scm.org/D11254

test-nointerrupt: make "sure" the handler "might" trigger (issue6558) We are sure that the signal got sent in the right time frame, however, we still have race, so either the code is actually buggy or we need some security to make sure the signal get processed. We might be affected by https://bugs.python.org/issue43406 ? Differential Revision: https://phab.mercurial-scm.org/D11251

testing: make sure write_file is "atomic" This make sure viewer cannot see the new file with partial content. This was likely the cause of some flakiness in `test-nointerrupt.t` Differential Revision: https://phab.mercurial-scm.org/D11250

test: disable test-subrepo-git.t in python2 + chg I am a couple of days in try to debug that at it seems minor enough with enough other priority to simply disable it for now. Differential Revision: https://phab.mercurial-scm.org/D11253