tests/test-sidedata.t

run-tests: introduce a `HGTEST_REAL_HG` variable for test

It turns out that currently, `hg` and `which hg` can point to different things
because `hg` is an alias… This is annoying because script and pieces of test
are unknowingly using the wrong `hg`.

We will fix it in another changeset. However some test actually need to use a
real `hg` binary and not some `chg` or `rhg` equivalent. So we introduce a new
variable with the right value and we put it to us in the appropriate location.

Differential Revision: https://phab.mercurial-scm.org/D11049

==========================================================
Test file dedicated to checking side-data related behavior
==========================================================

Check data can be written/read from sidedata
============================================

  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > testsidedata=$TESTDIR/testlib/ext-sidedata.py
  > EOF

  $ hg init test-sidedata --config experimental.revlogv2=enable-unstable-format-and-corrupt-my-data
  $ 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 experimental.revlogv2=no
  $ hg debugformat -v -R up-no-side-data
  format-variant     repo config default
  fncache:            yes    yes     yes
  dirstate-v2:         no     no      no
  dotencode:          yes    yes     yes
  generaldelta:       yes    yes     yes
  share-safe:          no     no      no
  sparserevlog:       yes    yes     yes
  persistent-nodemap:  no     no      no (no-rust !)
  persistent-nodemap: yes    yes      no (rust !)
  copies-sdc:          no     no      no
  revlog-v2:           no     no      no
  changelog-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 experimental.revlogv2=enable-unstable-format-and-corrupt-my-data
  format-variant     repo config default
  fncache:            yes    yes     yes
  dirstate-v2:         no     no      no
  dotencode:          yes    yes     yes
  generaldelta:       yes    yes     yes
  share-safe:          no     no      no
  sparserevlog:       yes    yes     yes
  persistent-nodemap:  no     no      no (no-rust !)
  persistent-nodemap: yes    yes      no (rust !)
  copies-sdc:          no     no      no
  revlog-v2:           no    yes      no
  changelog-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 debugupgraderepo -R up-no-side-data --config experimental.revlogv2=enable-unstable-format-and-corrupt-my-data > /dev/null

Check that we can downgrade from sidedata
-----------------------------------------

  $ hg init up-side-data --config experimental.revlogv2=enable-unstable-format-and-corrupt-my-data
  $ hg debugformat -v -R up-side-data
  format-variant     repo config default
  fncache:            yes    yes     yes
  dirstate-v2:         no     no      no
  dotencode:          yes    yes     yes
  generaldelta:       yes    yes     yes
  share-safe:          no     no      no
  sparserevlog:       yes    yes     yes
  persistent-nodemap:  no     no      no (no-rust !)
  persistent-nodemap: yes    yes      no (rust !)
  copies-sdc:          no     no      no
  revlog-v2:          yes     no      no
  changelog-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-side-data --config experimental.revlogv2=no
  format-variant     repo config default
  fncache:            yes    yes     yes
  dirstate-v2:         no     no      no
  dotencode:          yes    yes     yes
  generaldelta:       yes    yes     yes
  share-safe:          no     no      no
  sparserevlog:       yes    yes     yes
  persistent-nodemap:  no     no      no (no-rust !)
  persistent-nodemap: yes    yes      no (rust !)
  copies-sdc:          no     no      no
  revlog-v2:          yes     no      no
  changelog-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 debugupgraderepo -R up-side-data --config experimental.revlogv2=no > /dev/null