$ cat >> fakepager.py <<EOF

  > import sys

  > for line in sys.stdin:

  >     sys.stdout.write('paged! %r\n' % line)

  > 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 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'

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 = yes

  > [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 cmdutil, commands

  > cmdtable = {}

  > command = cmdutil.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

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