hg log --debug shouldn't show different data than {file_*} template keywords

https://bz.mercurial-scm.org/show_bug.cgi?id=6642

  $ hg init issue6642

  $ cd issue6642

  $ echo a > a

  $ hg ci -qAm a

  $ echo b > b

  $ hg ci -qAm b

  $ hg up 0 -q

  $ echo c > c

  $ hg ci -qAm c

  $ hg merge -q

  $ hg ci -m merge

  $ hg log -GT '{rev} {desc} file_adds: [{file_adds}], file_mods: [{file_mods}], file_dels: [{file_dels}], files: [{files}]\n'

  @    3 merge file_adds: [], file_mods: [], file_dels: [], files: []

  |\

  | o  2 c file_adds: [c], file_mods: [], file_dels: [], files: [c]

  | |

  o |  1 b file_adds: [b], file_mods: [], file_dels: [], files: [b]

  |/

  o  0 a file_adds: [a], file_mods: [], file_dels: [], files: [a]

  $ hg log -r . --debug | grep files

  [1]

  $ hg log -r . --debug -T json | egrep '(added|removed|modified)'

    "added": [],

    "modified": [],

    "removed": [],

  $ hg log -r . --debug -T xml | grep path

  <paths>

  </paths>