revlog-compression: use zstd by default (if available)
As see in changeset bb271ec2fbfb, zstd is 20% to 50% faster for reading and
writing.
Use take advantage of the new config behavior to try zstd by default, falling
back to zlib is zstd is not available on that plateform.
Differential Revision: https://phab.mercurial-scm.org/D10326
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Test file dedicated to checking side-data related behavior
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Check data can be written/read from sidedata
============================================
$ cat << EOF >> $HGRCPATH
> [extensions]
> testsidedata=$TESTDIR/testlib/ext-sidedata.py
> EOF
$ hg init test-sidedata --config format.exp-use-side-data=yes
$ cd test-sidedata
$ echo aaa > a
$ hg add a
$ hg commit -m a --traceback
$ echo aaa > b
$ hg add b
$ hg commit -m b
$ echo xxx >> a
$ hg commit -m aa
$ hg debugsidedata -c 0
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
$ hg debugsidedata -c 1 -v
2 sidedata entries
entry-0001 size 4
'\x00\x00\x006'
entry-0002 size 32
'\x98\t\xf9\xc4v\xf0\xc5P\x90\xf7wRf\xe8\xe27e\xfc\xc1\x93\xa4\x96\xd0\x1d\x97\xaaG\x1d\xd7t\xfa\xde'
$ hg debugsidedata -m 2
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
$ hg debugsidedata a 1
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
Check upgrade behavior
======================
Right now, sidedata has not upgrade support
Check that we can upgrade to sidedata
-------------------------------------
$ hg init up-no-side-data --config format.exp-use-side-data=no
$ hg debugformat -v -R up-no-side-data
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
share-safe: no no no
sparserevlog: yes yes yes
persistent-nodemap: no no no
copies-sdc: no no no
revlog-v2: no no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib (no-zstd !)
compression: zstd zstd zstd (zstd !)
compression-level: default default default
$ hg debugformat -v -R up-no-side-data --config format.exp-use-side-data=yes
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
share-safe: no no no
sparserevlog: yes yes yes
persistent-nodemap: no no no
copies-sdc: no no no
revlog-v2: no yes no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib (no-zstd !)
compression: zstd zstd zstd (zstd !)
compression-level: default default default
$ hg debugupgraderepo -R up-no-side-data --config format.exp-use-side-data=yes > /dev/null
Check that we can downgrade from sidedata
-----------------------------------------
$ hg init up-side-data --config format.exp-use-side-data=yes
$ hg debugformat -v -R up-side-data
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
share-safe: no no no
sparserevlog: yes yes yes
persistent-nodemap: no no no
copies-sdc: no no no
revlog-v2: yes no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib (no-zstd !)
compression: zstd zstd zstd (zstd !)
compression-level: default default default
$ hg debugformat -v -R up-side-data --config format.exp-use-side-data=no
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
share-safe: no no no
sparserevlog: yes yes yes
persistent-nodemap: no no no
copies-sdc: no no no
revlog-v2: yes no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib (no-zstd !)
compression: zstd zstd zstd (zstd !)
compression-level: default default default
$ hg debugupgraderepo -R up-side-data --config format.exp-use-side-data=no > /dev/null