compression: introduce an official `format.revlog-compression` option
This option supersedes the `experiment.format.compression` option. The value
currently supported are zlib (default) and zstd (if Mercurial was compiled with
zstd support).
The option gained an explicit reference to `revlog` since this is the target
usage here. Different storage methods might require different compression
strategies.
In our tests, using zstd give a significant CPU usage improvement (both
compression and decompressing) while keeping similar repository size.
Zstd as other interresting mode (dictionnary, pre-text, etc…) that are probably
worth exploring. However, just plain switching from zlib to zstd provide a large
benefit.
syntax: glob
*.elc
*.tmp
*.orig
*.rej
*~
*.mergebackup
*.o
*.so
*.dll
*.exe
*.pyd
*.pyc
*.pyo
*$py.class
*.swp
*.prof
*.zip
\#*\#
.\#*
tests/artifacts/cache/big-file-churn.hg
tests/.coverage*
tests/.testtimes*
tests/.hypothesis
tests/hypothesis-generated
tests/annotated
tests/exceptions
tests/*.err
tests/htmlcov
build
contrib/chg/chg
contrib/hgsh/hgsh
contrib/vagrant/.vagrant
dist
packages
doc/common.txt
doc/*.[0-9]
doc/*.[0-9].txt
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
MANIFEST.in
patches
mercurial/__modulepolicy__.py
mercurial/__version__.py
mercurial/hgpythonlib.h
mercurial.egg-info
.DS_Store
tags
cscope.*
.idea/*
.asv/*
i18n/hg.pot
locale/*/LC_MESSAGES/hg.mo
hgext/__index__.py
rust/target/
rust/*/target/
# Generated wheels
wheelhouse/
syntax: regexp
^\.pc/
^\.(pydev)?project
# hackable windows distribution additions
^hg-python
^hg.py$