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

rhg: handle broken pipe error for stderr Differential Revision: https://phab.mercurial-scm.org/D8871

rhg: extract function handle_stdout_error Avoid repeating the logic of handling stdout write errors. Differential Revision: https://phab.mercurial-scm.org/D8870