branching: merge stable into default for 6.9 cycle

Added signature for changeset 11f41248595b

Added tag 6.8 for changeset 11f41248595b

relnotes: add 6.8

test-check: don't report distutils as a local import On python 3.12 this is wrongly reported as a local import. So we adjust the checker to avoid it.

Backed out changeset f28c52a9f7b4 This backout and the previous are due to a large performance regression detected in repositories with a lot of obsmarkers when performing a clone. A better fix will come along at the start of the next cycle.

Backed out changeset ff523675cd69

rust: use `cpython` 0.7.2 crate to add support for Python 3.12 This will give us more headroom until we can migrate to PyO3 some day.

revbranchcache: disable mmap access by default The revbranchcache can be truncated (if some part of it is detected as invalid). Using mmap on file we truncate is not an option at access to truncated part would result in a SIGBUS signal. So we disable the mmap by default until we fix this issue.

portability: fix build on Solaris-derived systemd Current Illumos and older Solaris require _XOPEN_SOURCE for msg_control. O_DIRECTORY doesn't exist on older systems either, so fallback to O_RDONLY. It's good enough as a repository will require both R and X permission anyway.

mmap: only use mmap to read revlog persistent nodemap if it is safe Cf `is_mmap_safe` docstring.

mmap: fix another instance of reverse mmap logic in persistent nodemap This fix the same kind of issue as 85d96517e650

mmap: only use mmap to read rev-branch-cache data if it is safe Cf `is_mmap_safe` docstring.

mmap: only use mmap to read revlog index if it is safe Cf `is_mmap_safe` docstring.

mmap: add a `is_mmap_safe` method to vfs This will be useful to safeguard mmap usage to void SIGBUS when repositories lives on a NFS drive.

branching: merge stable into default

Added signature for changeset 6454c117c6a4

Added tag 6.8rc0 for changeset 6454c117c6a4

branching: merge default into stable for 6.8rc0

relnotes: add 6.8rc0

branch3: use an explicitely experimental name for files Since this format is still experimental, we don't want to have to side-step the `branch3` name in case people do start using it before it's stable.

obsolete: simplify relevantmarker Drop duplicate assignment from a merge failure. Save one loop iteration by exploiting that pendingnodes will be seennodes after the first round anyway, so just pre-initialize the set accordingly. From Anton Shestakov's review on !867. Performance difference for my test case is in the noise.

exchange: improve computation of relevant markers for large repos Find the candidates for nodes with relevant markers by going over all markers instead of iterating over all nodes. Most nodes will not have markers anyway. Further optimize the code by allowing revsets as well, which reduces the materialization cost.

test: better glob some timing related line to avoid flakiness If we go over 10 seconds, the number of white space changes.