tests/test-context-metadata.t

log: add -L/--line-range option to follow file history by line range

We add an experimental -L/--line-range option to 'hg log' taking file patterns
along with a line range using the (new) FILE,FROMLINE-TOLINE syntax where FILE
may be a pattern (matching exactly one file). The resulting history is similar
to what the "followlines" revset except that, if --patch is specified,
only diff hunks within specified line range are shown.

Basically, this brings the CLI on par with what currently only exists in hgweb
through line selection in "file" and "annotate" views resulting in a file log
with filtered patch to only display followed line range.

The option may be specified multiple times and can be combined with --rev and
regular file patterns to further restrict revisions. Usage of this option
requires --follow; revisions are shown in descending order and renames are
followed. Only the --graph option is currently not supported.

The UI is the result of a consensus from review feedback at:

  https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-October/106749.html


The implementation spreads between commands.log() and cmdutil module.
In commands.log(), the main loop may now use a "hunksfilter" factory (similar
to "filematcher") that, for a given "rev", produces a filtering function
for diff hunks for a given file context object.
The logic to build revisions from -L/--line-range options lives in
cmdutil.getloglinerangerevs() which produces "revs", "filematcher" and
"hunksfilter" information. Revisions obtained by following files' line range
are filtered if they do not match the revset specified by --rev option. If
regular FILE arguments are passed along with -L options, both filematchers are
combined into a new matcher.

.. feature::

   Add an experimental -L/--line-range FILE,FROMLINE-TOLINE option to 'hg log'
   command to follow the history of files by line range. In combination with
   -p/--patch option, only diff hunks within specified line range will be
   displayed. Feedback, especially on UX aspects, is welcome.

Tests about metadataonlyctx

  $ hg init
  $ echo A > A
  $ hg commit -A A -m 'Add A'
  $ echo B > B
  $ hg commit -A B -m 'Add B'
  $ hg rm A
  $ echo C > C
  $ echo B2 > B
  $ hg add C -q
  $ hg commit -m 'Remove A'

  $ cat > metaedit.py <<EOF
  > from __future__ import absolute_import
  > from mercurial import context, registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command('metaedit')
  > def metaedit(ui, repo, arg):
  >     # Modify commit message to "FOO"
  >     with repo.wlock(), repo.lock(), repo.transaction('metaedit'):
  >         old = repo['.']
  >         kwargs = dict(s.split('=', 1) for s in arg.split(';'))
  >         if 'parents' in kwargs:
  >             kwargs['parents'] = kwargs['parents'].split(',')
  >         new = context.metadataonlyctx(repo, old, **kwargs)
  >         new.commit()
  > EOF
  $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'text=Changed'
  $ hg log -r tip
  changeset:   3:ad83e9e00ec9
  tag:         tip
  parent:      1:3afb7afe6632
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     Changed
  
  $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'parents=0' 2>&1 | egrep '^RuntimeError'
  RuntimeError: can't reuse the manifest: its p1 doesn't match the new ctx p1

  $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'user=foo <[e-mail]>'
  $ hg log -r tip
  changeset:   4:1f86eaeca92b
  tag:         tip
  parent:      1:3afb7afe6632
  user:        foo <[e-mail]>
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     Remove A