mergestate: use collections.defaultdict(dict) for _stateextras I want to use this _stateextras more in upcoming patches to store some commit time related information. Using defaultdict will help in cleaner code around checking whether a file exists or not. Differential Revision: https://phab.mercurial-scm.org/D8919

hgweb: minimize scope of a try-block in staticfile() I think the exceptions are only relevant for the `os.stat()` and `open()` calls, and maybe to the `fh.read()` call. Differential Revision: https://phab.mercurial-scm.org/D8936

hgweb: ignore web.templates config when guessing mime type for static content Frozen binaries won't have a file-system path for static content, so I'd like to remove dependence on that. From the documentation, it seems like `mimetypes.guess_type()` only cares about the suffix, so I think it should be enough to pass in just path under the `web.templates` directory. Differential Revision: https://phab.mercurial-scm.org/D8935

hgweb: let staticfile() look up path from default location unless provided This reduces duplication between the two callers. Differential Revision: https://phab.mercurial-scm.org/D8934

hgweb: handle None from templatedir() equally bad in webcommands.py The following paragraph is based just on my reading of the code; I have not tried to test it. Before my recent work on templates in frozen binaries, it seems both `hgwebdir_mod.py` and `webcommands.py` would pass in an empty list into `staticfile()` when running in a frozen binary. That would then result in a variable in that function (`path`) not getting bound before its first use. I then changed that without thinking in D8786 so we passed a `None` value into the function, which made it break in another way (trying to iterate over `None`). Then I tried to fix it up in D8810, but I only changed `hgwebdir_mod.py` for some reason, and it still doesn't actually work in frozen binaries (which seems fair, since was broken before my changes too). This patch just replicates the half-assed "fix" from D8810 in `webcommands.py`, so they look more similar so I can start refactoring them in the same way. Differential Revision: https://phab.mercurial-scm.org/D8933

posixworker: avoid creating workers that end up getting no work If `workers` (the detected or configured number of CPUs) is greater than the number of work items, then some of the workers end up getting 0 work items. Let's not create such workers. Differential Revision: https://phab.mercurial-scm.org/D8927

revert: remove dangerous `parents` argument from `cmdutil.revert()` As we found out the hard way (thanks to spectral@ for figuring it out!), `cmdutil.revert()`'s `parents` argument must be `repo.dirstate.parents()` or things may go wrong. We had an extension that passed in the target commit as the first parent. The `hg split` command from the evolve extension seems to have made the same mistake, but I haven't looked carefully. The problem is that `cmdutil._performrevert()` calls `dirstate.normal()` on reverted files if the commit to revert to equals the first parent. So if you pass in `ctx=foo` and `parents=(foo.node(), nullid)`, then `dirstate.normal()` will be called for the revert files, even though they might not be clean in the working copy. There doesn't seem to be any reason, other than a tiny performance benefit, to passing the `parents` around instead of looking them up again in `cmdutil._performrevert()`, so that's what this patch does. Differential Revision: https://phab.mercurial-scm.org/D8925

requirements: introduce a set of working directory specific requirements Some requirements like the SPARSE_REQUIREMENT is working directory specific and cannot be shared. We add a set which will contain all these requirements. This is not the best we can do, I think having a rich requirement class will be much better but that will be out of scope for this series. Differential Revision: https://phab.mercurial-scm.org/D8924

localrepo: move requirements constant to requirements module We now have a dedicated module for requirements constant, let's move the ones in localrepo there. Differential Revision: https://phab.mercurial-scm.org/D8918

requirements: introduce new requirements related module It was not clear where all requirements should and related APIs should be, this patch introduces a requirements module which will have all exitsing requirements and related APIs. Differential Revision: https://phab.mercurial-scm.org/D8917

repository: introduce constant for treemanifest requirement and use it In future we will like to much cleaner logic around which requirement is for working copy and which can go in store. To start with that, we first need to de-clutter the requirement values spread around and replace them with constants. Differential Revision: https://phab.mercurial-scm.org/D8916

tests: make flag parsing test more future safe The revlog format contains a number of feature flags, e.g. if general deltas are active. When testing that unknown flags are rejected, use bits that are not immediately following the currently used bits. Differential Revision: https://phab.mercurial-scm.org/D8782

rename: add support for --at-rev, which marks as copy and removes the source I had previously only added support for `--at-rev` to `hg cp`, but not to `hg mv`. This patch adds that support. Just like for `hg cp`, it marks the destination as copied from the source, and doesn't care if the source file still exists (because it only supports the `-A` mode, aka "don't touch files" mode). It works whether or not the source file still exists. This matches the behavior of `hg mv -A` in the working copy. Differential Revision: https://phab.mercurial-scm.org/D8840

tests: make test-install.t work on debian systems Debian systems, at least as of their version of python3.8 on my machine, have rewritten some logic in ensurepip to make it not use the wheels in pip._bundled, but instead to use wheels installed in /usr/share/python-wheels. It copies these wheels into the virtual environment when it's created, and installenv/bin/pip is able to see them and use them, so it thinks that 'wheel' is installed, and that it can build the mercurial wheel instead of just installing it. For some reason, when it subprocesses to run `python3 setup.py bdist_wheel`, it setup.py does *not* have the 'wheel' wheel available, and we get an error message. Differential Revision: https://phab.mercurial-scm.org/D8813