tests/test-hgk.t

phabricator: warn if unable to amend, instead of aborting after posting

There was a divergence in behavior here between obsolete and strip based
amending.  I first noticed the abort when testing outside of the test harness,
but then had trouble recreating it here after reverting the code changes.  It
turns out, strip based amend was successfully amending the public commit after
it was posted!  It looks like the protection is in the `commit --amend` command,
not in the underlying code that it calls.

I considered doing a preflight check and aborting.  But the locks are only
acquired at the end, if amending, and this is too large a section of code to be
wrapped in a maybe-it's-held-or-not context manager for my tastes.
Additionally, some people do post-push reviews, and amending is the default
behavior, so they shouldn't see a misleading error message.

The lack of a 'Differential Revision' entry in the commit message breaks a
{phabreview} test, so it had to be partially conditionalized.

Minimal hgk check

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "hgk=" >> $HGRCPATH
  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg debug-cat-file commit 0
  tree a0c8bcbbb45c
  parent 000000000000
  author test 0 0
  revision 0
  branch default
  phase draft
  
  adda
  $ echo b > b
  $ hg ci -Am addb
  adding b
  $ hg log -T '{node}\n'
  102a90ea7b4a3361e4082ed620918c261189a36a
  07f4944404050f47db2e5c5071e0e84e7a27bba9

  $ hg debug-diff-tree 07f494440405 102a90ea7b4a
  :000000 100664 000000000000 1e88685f5dde N	b	b
  $ hg debug-diff-tree 07f494440405 102a90ea7b4a --patch
  diff --git a/b b/b
  new file mode 100644
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +b

Ensure that diff-tree output isn't affected by diffopts
  $ hg --config diff.noprefix=True debug-diff-tree 07f494440405 102a90ea7b4a
  :000000 100664 000000000000 1e88685f5dde N	b	b
  $ hg --config diff.noprefix=True debug-diff-tree --patch 07f494440405 102a90ea7b4a
  diff --git a/b b/b
  new file mode 100644
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +b

  $ cd ..