tests/test-issue6642.t

transaction: quietly rollback if no other changes than temporary files

If no actual change have been made, we don't really need to roll them back. We
only have to cleanup some temporary files and it seems reasonable to do that
quietly.

This will help us to use the transaction in wider context¹ without impacting the
user experience.

[1] as in Python context managers that lives longer.

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>