If the pqueue comparison fn returned just 0 or 1 (think "a<b")
then the sort order of returned items could be wrong because there
was a "< 0" that really needed to be "<= 0". Yikes!!!
This tweaks the pqueue_up and pqueue_down routines so that they
will not do full element swaps but instead carry over the state
of the previous loop iteration and only assign elements for which
we know the final position. This will avoid a little bit of data
assignment which should improve performance in theory.
Also got rid of some vector helpers that I'm no longer using.
This updates the git_pqueue to simply be a set of specialized
init/insert/pop functions on a git_vector.
To preserve the pqueue feature of having a fixed size heap, I
converted the "sorted" field in git_vectors to a more general
"flags" field so that pqueue could mix in it's own flag. This
had a bunch of ramifications because a number of places were
directly looking at the vector "sorted" field - I added a couple
new git_vector helpers (is_sorted, set_sorted) so the specific
representation of this information could be abstracted.
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.
The original libpqueue file were licensed under Apache 2.0 so
therefore should retain their copyrights and header as per the
license terms at http://www.apache.org/licenses/LICENSE-2.0
There were quite a few places were spaces were being used instead of
tabs. Try to catch them all. This should hopefully not break anything.
Except for `git blame`. Oh well.
1. The license header is technically not valid if it doesn't have a
copyright signature.
2. The COPYING file has been updated with the different licenses used in
the project.
3. The full GPLv2 header in each file annoys me.
The new revision walker uses an internal Commit object storage system,
custom memory allocator and much improved topological and time sorting
algorithms. It's about 20x times faster than the previous implementation
when browsing big repositories.
The following external API calls have changed:
`git_revwalk_next` returns an OID instead of a full commit object.
The initial call to `git_revwalk_next` is no longer blocking when
iterating through a repo with a time-sorting mode.
Iterating with Topological or inverted modes still makes the initial
call blocking to preprocess the commit list, but this block should be
mostly unnoticeable on most repositories (topological preprocessing
times at 0.3s on the git.git repo).
`git_revwalk_push` and `git_revwalk_hide` now take an OID instead
of a full commit object.
