Tree accessor tests with hard path names
Further tree building tests with hard paths
Update to latest clar
Merge pull request #2092 from libgit2/rb/update-clar

Update to latest clar
Add failing test case
Reflog: correct "new" id for reattaching HEAD
Check for errors when dereferencing symbolic refs
Add `git_reference_is_note`.
Merge pull request #2098 from arthurschreiber/arthur/add-git_reference_is_note

Add `git_reference_is_note`.
Merge pull request #2095 from libgit2/update-head-reflog

Correct "new" id for reattached-HEAD reflog entry
Reset helpers: use revparse instead
Add reflog parameters to git_reset
Fix warning
Add reset tests for reflog
Tests merge when changes exist in workdir/index
Tests merging staged files identical to result
Test that emulates a strange filter implementation
Merge wd validation tests against index not HEAD

Validating the workdir should not compare HEAD to working
directory - this is both inefficient (as it ignores the cache)
and incorrect.  If we had legitimately allowed changes in the
index (identical to the merge result) then comparing HEAD to
workdir would reject these changes as different.  Further, this
will identify files that were filtered strangely as modified,
while testing with the cache would prevent this.

Also, it's stupid slow.
Remove unused pointer assignment
Replace pqueue with code from hashsig heap

I accidentally wrote a separate priority queue implementation when
I was working on file rename detection as part of the file hash
signature calculation code.  To simplify licensing terms, I just
adapted that to a general purpose priority queue and replace the
old priority queue implementation that was borrowed from elsewhere.

This also removes parts of the COPYING document that no longer
apply to libgit2.