tests/test-export.t

localrepo: experimental support for non-zlib revlog compression

The final part of integrating the compression manager APIs into
revlog storage is the plumbing for repositories to advertise they
are using non-zlib storage and for revlogs to instantiate a non-zlib
compression engine.

The main intent of the compression manager work was to zstd all
of the things. Adding zstd to revlogs has proved to be more involved
than other places because revlogs are... special. Very small inputs
and the use of delta chains (which are themselves a form of
compression) are a completely different use case from streaming
compression, which bundles and the wire protocol employ. I've
conducted numerous experiments with zstd in revlogs and have yet
to formalize compression settings and a storage architecture that
I'm confident I won't regret later. In other words, I'm not yet
ready to commit to a new mechanism for using zstd - or any other
compression format - in revlogs.

That being said, having some support for zstd (and other compression
formats) in revlogs in core is beneficial. It can allow others to
conduct experiments.

This patch introduces *highly experimental* support for non-zlib
compression formats in revlogs. Introduced is a config option to
control which compression engine to use. Also introduced is a namespace
of "exp-compression-*" requirements to denote support for non-zlib
compression in revlogs. I've prefixed the namespace with "exp-"
(short for "experimental") because I'm not confident of the
requirements "schema" and in no way want to give the illusion of
supporting these requirements in the future. I fully intend to drop
support for these requirements once we figure out what we're doing
with zstd in revlogs.

A good portion of the patch is teaching the requirements system
about registered compression engines and passing the requested
compression engine as an opener option so revlogs can instantiate
the proper compression engine for new operations.

That's a verbose way of saying "we can now use zstd in revlogs!"

On an `hg pull` conversion of the mozilla-unified repo with no extra
redelta settings (like aggressivemergedeltas), we can see the impact
of zstd vs zlib in revlogs:

$ hg perfrevlogchunks -c
! chunk
! wall 2.032052 comb 2.040000 user 1.990000 sys 0.050000 (best of 5)
! wall 1.866360 comb 1.860000 user 1.820000 sys 0.040000 (best of 6)

! chunk batch
! wall 1.877261 comb 1.870000 user 1.860000 sys 0.010000 (best of 6)
! wall 1.705410 comb 1.710000 user 1.690000 sys 0.020000 (best of 6)

$ hg perfrevlogchunks -m
! chunk
! wall 2.721427 comb 2.720000 user 2.640000 sys 0.080000 (best of 4)
! wall 2.035076 comb 2.030000 user 1.950000 sys 0.080000 (best of 5)

! chunk batch
! wall 2.614561 comb 2.620000 user 2.580000 sys 0.040000 (best of 4)
! wall 1.910252 comb 1.910000 user 1.880000 sys 0.030000 (best of 6)

$ hg perfrevlog -c -d 1
! wall 4.812885 comb 4.820000 user 4.800000 sys 0.020000 (best of 3)
! wall 4.699621 comb 4.710000 user 4.700000 sys 0.010000 (best of 3)

$ hg perfrevlog -m -d 1000
! wall 34.252800 comb 34.250000 user 33.730000 sys 0.520000 (best of 3)
! wall 24.094999 comb 24.090000 user 23.320000 sys 0.770000 (best of 3)

Only modest wins for the changelog. But manifest reading is
significantly faster. What's going on?

One reason might be data volume. zstd decompresses faster. So given
more bytes, it will put more distance between it and zlib.

Another reason is size. In the current design, zstd revlogs are
*larger*:

debugcreatestreamclonebundle (size in bytes)
zlib: 1,638,852,492
zstd: 1,680,601,332

I haven't investigated this fully, but I reckon a significant cause of
larger revlogs is that the zstd frame/header has more bytes than
zlib's. For very small inputs or data that doesn't compress well, we'll
tend to store more uncompressed chunks than with zlib (because the
compressed size isn't smaller than original). This will make revlog
reading faster because it is doing less decompression.

Moving on to bundle performance:

$ hg bundle -a -t none-v2 (total CPU time)
zlib: 102.79s
zstd:  97.75s

So, marginal CPU decrease for reading all chunks in all revlogs
(this is somewhat disappointing).

$ hg bundle -a -t <engine>-v2 (total CPU time)
zlib: 191.59s
zstd: 115.36s

This last test effectively measures the difference between zlib->zlib
and zstd->zstd for revlogs to bundle. This is a rough approximation of
what a server does during `hg clone`.

There are some promising results for zstd. But not enough for me to
feel comfortable advertising it to users. We'll get there...

  $ hg init repo
  $ cd repo
  $ touch foo
  $ hg add foo
  $ for i in 0 1 2 3 4 5 6 7 8 9 10 11; do
  >    echo "foo-$i" >> foo
  >    hg ci -m "foo-$i"
  > done

  $ for out in "%nof%N" "%%%H" "%b-%R" "%h" "%r" "%m"; do
  >    echo
  >    echo "# foo-$out.patch"
  >    hg export -v -o "foo-$out.patch" 2:tip
  > done
  
  # foo-%nof%N.patch
  exporting patches:
  foo-01of10.patch
  foo-02of10.patch
  foo-03of10.patch
  foo-04of10.patch
  foo-05of10.patch
  foo-06of10.patch
  foo-07of10.patch
  foo-08of10.patch
  foo-09of10.patch
  foo-10of10.patch
  
  # foo-%%%H.patch
  exporting patches:
  foo-%617188a1c80f869a7b66c85134da88a6fb145f67.patch
  foo-%dd41a5ff707a5225204105611ba49cc5c229d55f.patch
  foo-%f95a5410f8664b6e1490a4af654e4b7d41a7b321.patch
  foo-%4346bcfde53b4d9042489078bcfa9c3e28201db2.patch
  foo-%afda8c3a009cc99449a05ad8aa4655648c4ecd34.patch
  foo-%35284ce2b6b99c9d2ac66268fe99e68e1974e1aa.patch
  foo-%9688c41894e6931305fa7165a37f6568050b4e9b.patch
  foo-%747d3c68f8ec44bb35816bfcd59aeb50b9654c2f.patch
  foo-%5f17a83f5fbd9414006a5e563eab4c8a00729efd.patch
  foo-%f3acbafac161ec68f1598af38f794f28847ca5d3.patch
  
  # foo-%b-%R.patch
  exporting patches:
  foo-repo-2.patch
  foo-repo-3.patch
  foo-repo-4.patch
  foo-repo-5.patch
  foo-repo-6.patch
  foo-repo-7.patch
  foo-repo-8.patch
  foo-repo-9.patch
  foo-repo-10.patch
  foo-repo-11.patch
  
  # foo-%h.patch
  exporting patches:
  foo-617188a1c80f.patch
  foo-dd41a5ff707a.patch
  foo-f95a5410f866.patch
  foo-4346bcfde53b.patch
  foo-afda8c3a009c.patch
  foo-35284ce2b6b9.patch
  foo-9688c41894e6.patch
  foo-747d3c68f8ec.patch
  foo-5f17a83f5fbd.patch
  foo-f3acbafac161.patch
  
  # foo-%r.patch
  exporting patches:
  foo-02.patch
  foo-03.patch
  foo-04.patch
  foo-05.patch
  foo-06.patch
  foo-07.patch
  foo-08.patch
  foo-09.patch
  foo-10.patch
  foo-11.patch
  
  # foo-%m.patch
  exporting patches:
  foo-foo_2.patch
  foo-foo_3.patch
  foo-foo_4.patch
  foo-foo_5.patch
  foo-foo_6.patch
  foo-foo_7.patch
  foo-foo_8.patch
  foo-foo_9.patch
  foo-foo_10.patch
  foo-foo_11.patch

Doing it again clobbers the files rather than appending:
  $ hg export -v -o "foo-%m.patch" 2:3
  exporting patches:
  foo-foo_2.patch
  foo-foo_3.patch
  $ grep HG foo-foo_2.patch | wc -l
  \s*1 (re)
  $ grep HG foo-foo_3.patch | wc -l
  \s*1 (re)

Exporting 4 changesets to a file:

  $ hg export -o export_internal 1 2 3 4
  $ grep HG export_internal | wc -l
  \s*4 (re)

Doing it again clobbers the file rather than appending:
  $ hg export -o export_internal 1 2 3 4
  $ grep HG export_internal | wc -l
  \s*4 (re)

Exporting 4 changesets to stdout:

  $ hg export 1 2 3 4 | grep HG | wc -l
  \s*4 (re)

Exporting revision -2 to a file:

  $ hg export -- -2
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 5f17a83f5fbd9414006a5e563eab4c8a00729efd
  # Parent  747d3c68f8ec44bb35816bfcd59aeb50b9654c2f
  foo-10
  
  diff -r 747d3c68f8ec -r 5f17a83f5fbd foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -8,3 +8,4 @@
   foo-7
   foo-8
   foo-9
  +foo-10

No filename should be printed if stdout is specified explicitly:

  $ hg export -v 1 -o -
  exporting patch:
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID d1c9656e973cfb5aebd5499bbd2cb350e3b12266
  # Parent  871558de6af2e8c244222f8eea69b782c94ce3df
  foo-1
  
  diff -r 871558de6af2 -r d1c9656e973c foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,2 @@
   foo-0
  +foo-1

Checking if only alphanumeric characters are used in the file name (%m option):

  $ echo "line" >> foo
  $ hg commit -m " !\"#$%&(,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]"'^'"_\`abcdefghijklmnopqrstuvwxyz{|}~"
  $ hg export -v -o %m.patch tip
  exporting patch:
  ____________0123456789_______ABCDEFGHIJKLMNOPQRSTUVWXYZ______abcdefghijklmnopqrstuvwxyz____.patch

Catch exporting unknown revisions (especially empty revsets, see issue3353)

  $ hg export
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 197ecd81a57f760b54f34a58817ad5b04991fa47
  # Parent  f3acbafac161ec68f1598af38f794f28847ca5d3
   !"#$%&(,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
  
  diff -r f3acbafac161 -r 197ecd81a57f foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -10,3 +10,4 @@
   foo-9
   foo-10
   foo-11
  +line

  $ hg export ""
  hg: parse error: empty query
  [255]
  $ hg export 999
  abort: unknown revision '999'!
  [255]
  $ hg export "not all()"
  abort: export requires at least one changeset
  [255]

Check for color output
  $ cat <<EOF >> $HGRCPATH
  > [color]
  > mode = ansi
  > [extensions]
  > color =
  > EOF

  $ hg export --color always --nodates tip
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID * (glob)
  # Parent * (glob)
   !"#$%&(,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
  
  \x1b[0;1mdiff -r f3acbafac161 -r 197ecd81a57f foo\x1b[0m (esc)
  \x1b[0;31;1m--- a/foo\x1b[0m (esc)
  \x1b[0;32;1m+++ b/foo\x1b[0m (esc)
  \x1b[0;35m@@ -10,3 +10,4 @@\x1b[0m (esc)
   foo-9
   foo-10
   foo-11
  \x1b[0;32m+line\x1b[0m (esc)


  $ cd ..