tests/test-children.t

zsh_completion: declare appropriate local parameters for ->string form

When ->string form is used for _arguments, the function that calls it must
declare appropriate local parameters.

Managing local return value is needed to tell the completion system if our
function succeeded in suggesting something or not, plus without that `hg diff
-<TAB>` doesn't look right.

While at it, fix a copypaste error (s/diff_files/revert_files/).

Docs: http://zsh.sourceforge.net/Doc/Release/Completion-System.html

Differential Revision: https://phab.mercurial-scm.org/D4264

test children command

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > children =
  > EOF

init
  $ hg init t
  $ cd t

no working directory
  $ hg children

setup
  $ echo 0 > file0
  $ hg ci -qAm 0 -d '0 0'

  $ echo 1 > file1
  $ hg ci -qAm 1 -d '1 0'

  $ echo 2 >> file0
  $ hg ci -qAm 2 -d '2 0'

  $ hg co null
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo 3 > file3
  $ hg ci -qAm 3 -d '3 0'

hg children at revision 3 (tip)
  $ hg children

  $ hg co null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

hg children at nullrev (should be 0 and 3)
  $ hg children
  changeset:   0:4df8521a7374
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     0
  
  changeset:   3:e2962852269d
  tag:         tip
  parent:      -1:000000000000
  user:        test
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     3
  
  $ hg co 1
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

hg children at revision 1 (should be 2)
  $ hg children
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  
  $ hg co 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

hg children at revision 2 (other head)
  $ hg children

  $ for i in null 0 1 2 3 '2^'; do
  > echo "hg children -r '$i'"
  > hg children -r $i
  > done
  hg children -r 'null'
  changeset:   0:4df8521a7374
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     0
  
  changeset:   3:e2962852269d
  tag:         tip
  parent:      -1:000000000000
  user:        test
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     3
  
  hg children -r '0'
  changeset:   1:708c093edef0
  user:        test
  date:        Thu Jan 01 00:00:01 1970 +0000
  summary:     1
  
  hg children -r '1'
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  
  hg children -r '2'
  hg children -r '3'
  hg children -r '2^'
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  

hg children -r 0 file0 (should be 2)
  $ hg children -r 0 file0
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  

hg children -r 1 file0 (should be 2)
  $ hg children -r 1 file0
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  

  $ hg co 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

hg children file0 at revision 0 (should be 2)
  $ hg children file0
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  

should be compatible with templater (don't pass fctx to displayer)
  $ hg children file0 -Tdefault
  changeset:   2:8f5eea5023c2
  user:        test
  date:        Thu Jan 01 00:00:02 1970 +0000
  summary:     2
  

  $ cd ..