issue6528: add a config option to control the fixing on the fly This will allow people who know to be safe to avoid any performance overhead (and other potential issue). Differential Revision: https://phab.mercurial-scm.org/D11271

issue6528: also filter delta on the fly when applying a changegroup This ensure that corrupted clone does not spread corruption to "fixed" version. This might come at a performance cost, we will had a config option to control this behavior in the next changesets. Differential Revision: https://phab.mercurial-scm.org/D11270

filelog: open the writing context a bit earlier in `addgroup` This is a small change made ahead of the next patch for clarification. Differential Revision: https://phab.mercurial-scm.org/D11269

issue6528: implement _is_revision_affected_fast using callback The delta comming from a bundle/stream does not exists in the revlog yet, so we will need other way to retrieve the same information. To prepare for this we split the function to use callbacks in the core logic. Differential Revision: https://phab.mercurial-scm.org/D11268

issue6528: implement _is_revision_affected using callback The delta comming from a bundle/stream does not exists in the revlog yet, so we will need other way to retrieve the same information. To prepare for this we split the function to use callbacks in the core logic. Differential Revision: https://phab.mercurial-scm.org/D11267

debugcommands: add a `--paranoid` option to `debug-repair-issue-6528` See justification inline. Differential Revision: https://phab.mercurial-scm.org/D11263

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