relnotes/6.9

clone: properly exclude rev-branch-cache from post clone cache warming

When adding "CACHE_REV_BRANCH" to "CACHES_ALL" in e51161b12c7e, I did not
expected it to impact the clone steps. However the "CACHES_POST_CLONE" set is
created rather creatively. (we should fix that, but not on stable)

The benchmark caught a quite significant slowdown one hardlink and ssh-stream
clones. Such slow down can be reduced to around ~5% by fully warming the cache
before the clone. However keeping this expensive step away from the clone
operation fully fix the slowdown and preserve the initial intend.


Example slowdow for hardlink clone

### benchmark.name                               = hg.command.clone
  # bin-env-vars.hg.flavor                       = default
  # bin-env-vars.hg.py-re2-module                = default
  # benchmark.variants.explicit-rev              = none
  # benchmark.variants.issue6528                 = default
  # benchmark.variants.protocol                  = local-hardlink
  # benchmark.variants.pulled-delta-reuse-policy = default
  # benchmark.variants.resource-usage            = default
  # benchmark.variants.validate                  = default
 ## data-env-vars.name = netbeans-2018-08-01-zstd-sparse-revlog
6.8.2:  19.799752
6.9rc0: 29.017493  (+46.55%, +9.22)
after:  19.929341

 ## data-env-vars.name = mercurial-public-2018-08-01-zstd-sparse-revlog
6.8.2:  0.468020
6.9rc0: 1.701294 (+263.51%, +1.23)
after:  0.471934

 ## data-env-vars.name = pypy-2024-03-22-zstd-sparse-revlog
6.8.2:  2.397564
6.9rc0: 5.666641 (+137.41%, +3.28)
after:  2.428085

= Mercurial 6.9rc0 =

/!\ These are release notes for a release candidate version. Any and all points can be reverted before the final release.

== New Features ==

 * exchange: improve computation of relevant markers for large repos
 * Add a Rust fast-path to speed up update (also for `clone`) from null (up to 4x faster) 
 * Introduced a new rev-branch-cache version (v2) that is mmap-resistant
 * The branchmap's performance was improved
 * Improved the performance of the fix for issue6528
 * clonebundles: allow manifest to specify sha256 digest of bundles
 * merge: improve working-copy mtime race handling
 * profiling: add a py-spy profiling backend
 * revlog: use an explicit config option to enable mmap usage for index
 * revlog: use mmap by default is pre-population is available
 * mmap: populate the mapping by default
 * mmap: populate mapping in a background thread

== Experimental features ==

 * merge: add a config to allow conflict-free merge of changes on adjacent lines

== Bug Fixes ==

 * `config.server.validate` now also works on narrowed repositories
 * convert: fix various leaked file descriptors
 * stream: prefer keeping an open file handle to volatile file instead of copy
 * dummysmtpd: fix EOF handling on newer versions of OpenSSL
 * cext: correct the argument handling of `b85encode()`
 * branchmap-v3: make sure we write the cache after detecting pure-topo mode
 * rust: apply clippy lints
 * copies: make sure deleted copy info do not overwriting unrelated ones
 * rebase: don't call rewriteutil.precheck() with to-be-skipped commits
 * phabricator: correct the default value of `phabhunk.corpus`
 * linelog: correct the default value of `annotateresult.lines`
 * largefiles: avoid a potentially undefined variable in exception case
 * httppeer: move a variable to avoid a bad reference before assignment warning
 * httppeer: avoid another bad reference before assignment warning
 * tests: use packaging from setuptools instead of deprecated distutils
 * manifest: type and fix unhexlify
 * manifest: align some vfs option access on the fact we might not have options
 * scmutils: read the requires file before writing to avoid unnecessary rewrite
 * debugsparse: stop taking the store lock
 * sparse: reliably avoid writing to store without a lock
 * largefiles: sync up `largefilesdirstate` methods with `dirstate` base class
 * shelve: raise an error when loading a corrupt state file in an impossible case
 * monotone: replace %s interpolation with appropriate numeric specifiers
 * shelve: consistently convert exception to bytes via `stringutil.forcebytestr`
 * remotefilelog: honor the `--format` arg of the `debugindex` command
 * remotefilelog: adapt the `debugindex` command to past API changes
 * run-tests: add color to the progress output
 * archive: defer opening the output until a file is matched
 * help: add :config-doc:`section.key` shorthand to insert documentation
 * censor: document the censor.policy option (issue6909)
 * rust-revlog: don't try to open the data file if the index is empty
 * bundlerepo: fix mismatches with repository and revlog classes
 * revlog: make `clearcaches()` signature consistent with ManifestRevlog
 * unionrepo: fix mismatches with revlog classes
 * keepalive: fix a signature mismatch for a http.client.HTTPResponse subclass
 * lfs: fix various signature mismatches for vfs subclasses
 * store: fix a signature mismatch for a vfs subclass
 * util: avoid a leaked file descriptor in `util.makelock()` exceptional case
 * statichttprepo: fix `httprangereader.read()` for py3
 * util: make `mmapread()` work on Windows again
 * mdiff: tweak calls into `bdiff.fixws` to match its type hints
 * base85: avoid a spurious use-before-initialized warning in `pure` module
 * install: static data moved from setup.py to pyproject.toml
 * upgrade: disable using the parallel workers optimization on macOS
 * doc: generate separate commands/topics/extension pages
 * extdiff: don't run gui programs when in a cli-only environment
 * clonebundles: stop shell quoting `HGCB_BUNDLE_BASENAME` environment variable
 * rev-branch-cache: disable mmapping by default on Windows

== Backwards Compatibility Changes ==

 * This release drops support for Python 3.6 and 3.7.

== Internal API Changes ==

 * manifest: deprecated readdelta and readfast

== Miscellaneous ==

 * http: reuse Python's implementation of read/readline/readinto
 * http: use urllib's cookie handler
 * rev-branch-cache: schedule a write of the "v2" format if we read from "v1"
 * rev-branch-cache: have debugupdatecache warm rbc too
 * rev-branch-cache: reenable memory mapping of the revision data
 * debugwireproto: redo logging to also work for https
 * rust: use `.cargo/config.toml` instead of `.cargo/config`
 * A whole bunch of typing improvements, which in turn found many bugs
 * Test suite improvements
 * Various packaging improvements