tests/test-issue6642.t

emitrevision: if we need to compute a delta on the fly, try p1 or p2 first

Falling back to `prev` does not yield any real value on modern storage and
result in pathological changes to be created on the other side. Doing a delta
against a parent will likely be smaller (helping the network) and will be safer
to apply on the client (helping future pulls by Triggering intermediate
snapshop where they will be needed by later deltas).

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>