tests/test-pager.t

revlog: skeleton support for version 2 revlogs

There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.

It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.

This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.

An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.

To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.

Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.

There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.

  $ cat >> fakepager.py <<EOF
  > import sys
  > printed = False
  > for line in sys.stdin:
  >     sys.stdout.write('paged! %r\n' % line)
  >     printed = True
  > if not printed:
  >     sys.stdout.write('paged empty output!\n')
  > EOF

Enable ui.formatted because pager won't fire without it, and set up
pager and tell it to use our fake pager that lets us see when the
pager was running.
  $ cat >> $HGRCPATH <<EOF
  > [ui]
  > formatted = yes
  > color = no
  > [pager]
  > pager = python $TESTTMP/fakepager.py
  > EOF

  $ hg init repo
  $ cd repo
  $ echo a >> a
  $ hg add a
  $ hg ci -m 'add a'
  $ for x in `python $TESTDIR/seq.py 1 10`; do
  >   echo a $x >> a
  >   hg ci -m "modify a $x"
  > done

By default diff and log are paged, but id is not:

  $ hg diff -c 2 --pager=yes
  paged! 'diff -r f4be7687d414 -r bce265549556 a\n'
  paged! '--- a/a\tThu Jan 01 00:00:00 1970 +0000\n'
  paged! '+++ b/a\tThu Jan 01 00:00:00 1970 +0000\n'
  paged! '@@ -1,2 +1,3 @@\n'
  paged! ' a\n'
  paged! ' a 1\n'
  paged! '+a 2\n'

  $ hg log --limit 2
  paged! 'changeset:   10:46106edeeb38\n'
  paged! 'tag:         tip\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 10\n'
  paged! '\n'
  paged! 'changeset:   9:6dd8ea7dd621\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 9\n'
  paged! '\n'

  $ hg id
  46106edeeb38 tip

We can control the pager from the config

  $ hg log --limit 1 --config 'ui.paginate=False'
  changeset:   10:46106edeeb38
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a 10
  
  $ hg log --limit 1 --config 'ui.paginate=0'
  changeset:   10:46106edeeb38
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a 10
  
  $ hg log --limit 1 --config 'ui.paginate=1'
  paged! 'changeset:   10:46106edeeb38\n'
  paged! 'tag:         tip\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 10\n'
  paged! '\n'

We can enable the pager on id:

BROKEN: should be paged
  $ hg --config pager.attend-id=yes id
  46106edeeb38 tip

Setting attend-$COMMAND to a false value works, even with pager in
core:
  $ hg --config pager.attend-diff=no diff -c 2
  diff -r f4be7687d414 -r bce265549556 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,2 +1,3 @@
   a
   a 1
  +a 2

Command aliases should have same behavior as main command

  $ hg history --limit 2
  paged! 'changeset:   10:46106edeeb38\n'
  paged! 'tag:         tip\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 10\n'
  paged! '\n'
  paged! 'changeset:   9:6dd8ea7dd621\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 9\n'
  paged! '\n'

Abbreviated command alias should also be paged

  $ hg hist -l 1
  paged! 'changeset:   10:46106edeeb38\n'
  paged! 'tag:         tip\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 10\n'
  paged! '\n'

Attend for an abbreviated command does not work

  $ hg --config pager.attend-ident=true ident
  46106edeeb38 tip

  $ hg --config extensions.pager= --config pager.attend-ident=true ident
  46106edeeb38 tip

Pager should not start if stdout is not a tty.

  $ hg log -l1 -q --config ui.formatted=False
  10:46106edeeb38

Pager should be disabled if pager.pager is empty (otherwise the output would
be silently lost.)

  $ hg log -l1 -q --config pager.pager=
  10:46106edeeb38

Pager with color enabled allows colors to come through by default,
even though stdout is no longer a tty.
  $ cat >> $HGRCPATH <<EOF
  > [ui]
  > color = always
  > [color]
  > mode = ansi
  > EOF
  $ hg log --limit 3
  paged! '\x1b[0;33mchangeset:   10:46106edeeb38\x1b[0m\n'
  paged! 'tag:         tip\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 10\n'
  paged! '\n'
  paged! '\x1b[0;33mchangeset:   9:6dd8ea7dd621\x1b[0m\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 9\n'
  paged! '\n'
  paged! '\x1b[0;33mchangeset:   8:cff05a6312fe\x1b[0m\n'
  paged! 'user:        test\n'
  paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
  paged! 'summary:     modify a 8\n'
  paged! '\n'

An invalid pager command name is reported sensibly if we don't have to
use shell=True in the subprocess call:
  $ hg log --limit 3 --config pager.pager=this-command-better-never-exist
  missing pager command 'this-command-better-never-exist', skipping pager
  \x1b[0;33mchangeset:   10:46106edeeb38\x1b[0m (esc)
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a 10
  
  \x1b[0;33mchangeset:   9:6dd8ea7dd621\x1b[0m (esc)
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a 9
  
  \x1b[0;33mchangeset:   8:cff05a6312fe\x1b[0m (esc)
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a 8
  

A complicated pager command gets worse behavior. Bonus points if you can
improve this.
  $ hg log --limit 3 \
  >   --config pager.pager='this-command-better-never-exist --seriously' \
  >  2>/dev/null || true

Pager works with shell aliases.

  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > echoa = !echo a
  > EOF

  $ hg echoa
  a
BROKEN: should be paged
  $ hg --config pager.attend-echoa=yes echoa
  a

Pager works with hg aliases including environment variables.

  $ cat >> $HGRCPATH <<'EOF'
  > [alias]
  > printa = log -T "$A\n" -r 0
  > EOF

  $ A=1 hg --config pager.attend-printa=yes printa
  paged! '1\n'
  $ A=2 hg --config pager.attend-printa=yes printa
  paged! '2\n'

Something that's explicitly attended is still not paginated if the
pager is globally set to off using a flag:
  $ A=2 hg --config pager.attend-printa=yes printa --pager=no
  2

Pager should not override the exit code of other commands

  $ cat >> $TESTTMP/fortytwo.py <<'EOF'
  > from mercurial import commands, registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command('fortytwo', [], 'fortytwo', norepo=True)
  > def fortytwo(ui, *opts):
  >     ui.write('42\n')
  >     return 42
  > EOF

  $ cat >> $HGRCPATH <<'EOF'
  > [extensions]
  > fortytwo = $TESTTMP/fortytwo.py
  > EOF

  $ hg fortytwo --pager=on
  paged! '42\n'
  [42]

A command that asks for paging using ui.pager() directly works:
  $ hg blame a
  paged! ' 0: a\n'
  paged! ' 1: a 1\n'
  paged! ' 2: a 2\n'
  paged! ' 3: a 3\n'
  paged! ' 4: a 4\n'
  paged! ' 5: a 5\n'
  paged! ' 6: a 6\n'
  paged! ' 7: a 7\n'
  paged! ' 8: a 8\n'
  paged! ' 9: a 9\n'
  paged! '10: a 10\n'
but not with HGPLAIN
  $ HGPLAIN=1 hg blame a
   0: a
   1: a 1
   2: a 2
   3: a 3
   4: a 4
   5: a 5
   6: a 6
   7: a 7
   8: a 8
   9: a 9
  10: a 10
explicit flags work too:
  $ hg blame --pager=no a
   0: a
   1: a 1
   2: a 2
   3: a 3
   4: a 4
   5: a 5
   6: a 6
   7: a 7
   8: a 8
   9: a 9
  10: a 10

A command with --output option:

  $ hg cat -r0 a
  paged! 'a\n'
  $ hg cat -r0 a --output=-
  paged! 'a\n'
  $ hg cat -r0 a --output=out
  $ rm out

Put annotate in the ignore list for pager:
  $ cat >> $HGRCPATH <<EOF
  > [pager]
  > ignore = annotate
  > EOF
  $ hg blame a
   0: a
   1: a 1
   2: a 2
   3: a 3
   4: a 4
   5: a 5
   6: a 6
   7: a 7
   8: a 8
   9: a 9
  10: a 10

Environment variables like LESS and LV are set automatically:
  $ cat > $TESTTMP/printlesslv.py <<EOF
  > import os, sys
  > sys.stdin.read()
  > for name in ['LESS', 'LV']:
  >     sys.stdout.write(('%s=%s\n') % (name, os.environ.get(name, '-')))
  > sys.stdout.flush()
  > EOF

  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > noop = log -r 0 -T ''
  > [ui]
  > formatted=1
  > [pager]
  > pager = $PYTHON $TESTTMP/printlesslv.py
  > EOF
  $ unset LESS
  $ unset LV
  $ hg noop --pager=on
  LESS=FRX
  LV=-c
  $ LESS=EFGH hg noop --pager=on
  LESS=EFGH
  LV=-c