The method returns an int with the amount of objects free'd

One of my brainfarts made me export it as `git_repository_close` instead
of GC. Duh.

That way non-C bindings can use it.

The commit list was not being properly free'd when a walk was stopped
halfway through.

We now depend on libpthread on all Unix platforms (should be installed
by default) and use a simple wrapper for Windows threads under Win32.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Yes, we are changing the Zlib code. This is dangerous and uncool.
Fortunately, these are just some implicit casts.

I don't know if this is good or bad. This lets libgit2 compile cleanly
on any platforms without any external dependencies, but adds a little
bit of bloat...

Let's test this out and see what happens.

A version *so* awesome that needs 2 version bumps AND a codename.

Major features:

	- New internal garbage collection (harder)
	- Pack backend rewritten from scratch (better)
	- Revision walker rewritten from scratch (faster)
	- New object interdependency system (stronger)
	- Unique OID shortener
	- Reference listing

In honor of one heck of a music album, released ten years ago,
yesterday.

It's no longer retarded. All object interdependencies are stored as OIDs
instead of actual objects. This should be hundreds of times faster,
specially on big repositories. Heck, who knows, maye it doesn't even
segfault -- wouldn't that be awesome?

What has changed on the API?

	`git_commit_parent`, `git_commit_tree`, `git_tag_target` now return
	their values through a pointer-to-pointer, and have an error code.

	`git_commit_set_tree` and `git_tag_set_target` now return an error
	code and may fail.

	`git_repository_free__no_gc` has been deprecated because it's
	stupid. Since there are no longer any interdependencies between
	objects, we don't need internal reference counting, and GC
	never fails or double-free's pointers.

	`git_object_close` now does a very sane thing: marks an object
	as unused. Closed objects will be eventually free'd from the
	object cache based on LRU. Please use `git_object_close` from
	the garbage collector `destroy` method on your bindings. It's
	100% safe.

	`git_repository_gc` is a new method that forces a garbage collector
	pass through the repo, to free as many LRU objects as possible.
	This is useful if we are running out of memory.

Lists all the references in a repository. Listing may be filtered by
reference type.

This should applease Lord Clem.

The new pack backend is an adaptation of the original git.git code in
`sha1_file.c`. It's slightly faster than the previous version and
severely less memory-hungry.

The call-stack of a normal pack backend query has been properly
documented in the top of the header for future reference. And by
properly I mean with ASCII diagrams 'n shit.

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.

Set of methods to find the minimal-length to uniquely identify every OID
in a list. Useful for GUI applications, commit logs and so on.

Includes stress test.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Use a new `gitfo_creat_force` that will create the full path to a file
before creating it.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

We cannot make sure that the user doesn't use the same buffer as source
and destination, so write to it using memmove.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Should return `void *` for raw bytes.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

We were checking for the index file, which is not assured to exist on
clean git repositories.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

add actual must_pass calls back into the repo tests and remove ./ from
beginning of temp repo path

Disable garbage collection of cross-references to prevent
double-freeing. Internal reference management is now done
with a separate method.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

They are not standard. MSVC complains about them. And that's not good.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Signed-off-by: Vicent Marti <tanoku@gmail.com>

MSVC cannot substract void pointers. Go figure.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Yes, these are some seriously massive changes to the external API. We
are breaking stuff.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

Signed-off-by: Vicent Marti <tanoku@gmail.com>

- Added several missing reference increases
- Add new destructor to the repository that does not GC the objects

Signed-off-by: Vicent Marti <tanoku@gmail.com>