Post 2.45.2 updates
Merge down a handful of topics to adjust tests and CI to make them
work better, without changing Git itself, and a bit of developer
docs update:
* Tests that try to corrupt in-repository files in chunked format did
not work well on macOS due to its broken "mv", which has been
worked around.
* Unbreak CI jobs so that we do not attempt to use Python 2 that has
been removed from the platform.
* Git 2.43 started using the tree of HEAD as the source of attributes
in a bare repository, which has severe performance implications.
For now, revert the change, without ripping out a more explicit
support for the attr.tree configuration variable.
* Windows CI running in GitHub Actions started complaining about the
order of arguments given to calloc(); the imported regex code uses
the wrong order almost consistently, which has been corrected.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
