D779: merge: add _checkunknowndirs function for detecting path conflicts

[mbthomas (Mark Thomas)]

mbthomas added inline comments.

INLINE COMMENTS

> ryanmce wrote in merge.py:654
> Why do we need to audit this path first? If we fail the audit, what happens? This looks weird to me.

As in `_checkunknownfile`, this is to avoid symlink traversal while checking these files.

Consider:

  $ ln -s bar foo
  $ hg add foo
  $ hg up <some revision where foo is a directory containing directories>

When checking `foo/dir1/file1`, we will go through `foo` then `foo/dir1` in this loop.  The first case doesn't trigger the rule, as although `foo` is a link, it's in the dirstate, so should have been resolved by the merge.  The second loop will dereference `foo` and look at `bar/dir1`, which we don't want it to do.

Doing nothing is the right thing here - we will resolve the pathconflict via the merge resolution (there will be a `'pr'` action for this link).

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D779

To: mbthomas, #hg-reviewers
Cc: ryanmce, mercurial-devel