The following methods have been implemented:

	git_reference_packall
	git_reference_rename
	git_reference_delete

The library now has full support for packed references, including
partial and total writing. Internal documentation has been updated with
the details.

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

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

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

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

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

These two reference types are now stored separately to eventually allow
the removal/renaming of loose references and rewriting of the refs
packfile.

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

Changed some more API details and updated documentation.

Sketched API for addition/removal of entries.

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

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

This makes generating bindings to hlibgit2 easier

We now use MoveFileEx, which is not assured to be atomic but works for
always (both if the destination exists, or if it doesn't) and is
available in MinGW.

Since this is a Win32 API call, complaint about lost or overwritten files
should be forwarded at Steve Ballmer.

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

The `rename` call doesn't quite work on Win32: expects the destination
file to not exist. We're using a native Win32 call in those cases --
that should do the trick.

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

Was crashing the Windows build.

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

The old hash table with chained buckets has been replaced by a new one
using Cuckoo hashing, which offers guaranteed constant lookup times.
This should improve speeds on most use cases, since hash tables in
libgit2 are usually used as caches where the objects are stored once and
queried several times.

The Cuckoo hash implementation is based off the one in the Basekit
library [1] for the IO language, but rewritten to support an arbritrary
number of hashes. We currently use 3 to maximize the usage of the nodes pool.

[1]: https://github.com/stevedekorte/basekit/blob/master/source/CHash.c

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

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

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

Disable sqlite support when ./waf configure is run with --without-sqlite

The new `git_filebuf` structure provides atomic high-performance writes
to disk by using a write cache, and optionally a double-buffered scheme
through a worker thread (not enabled yet).

Writes can be done 3-layered, like in git.git (user code -> write cache
-> disk), or 2-layered, by writing directly on the cache. This makes
index writing considerably faster.

The `git_filebuf` structure contains all the old functionality of
`git_filelock` for atomic file writes and reads. The `git_filelock`
structure has been removed.

Additionally, the `git_filebuf` API allows to automatically hash (SHA1)
all the data as it is written to disk (hashing is done smartly on big
chunks to improve performance).

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

Fixed several issues with path joining and bare repos.

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

The `prev` and `next` pointers were not being updated after popping one
of the list elements.

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

The interlocking on the write threads was not being done properly (index
entries were sometimes written out of order). With proper interlocking,
the threaded write is only marginally faster on big index files, and
slower on the smaller ones because of the overhead when creating
threads.

The threaded index writing has been temporarily disabled; after more
accurate benchmarks, if might be possible to enable it again only when
writing very large index files (> 1000 entries).

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

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

64-bit types stored in memory have to be truncated into 32 bits when
writing to disk. Was causing warnings in MSVC.

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

In response to issue #60 (git_index_write really slow), the write_index
function has been rewritten to improve its performance -- it should now
be in par with the performance of git.git.

On top of that, if Posix Threads are available when compiling libgit2, a
new threaded writing system will be used (3 separate threads take care
of solving byte-endianness, hashing the contents of the index and
writing to disk, respectively). For very long Index files, this method
is up to 3x times faster than git.git.

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

git_tag_lookup() and git_tag_new() changed to cast GIT_OBJ_TAG to
git_otype in order to compile lib in xcode

The priority value for different backends has been removed from the
public `git_odb_backend` struct. We handle that internally. The priority
value is specified on the `git_odb_add_alternate`.

This is convenient because it allows us to poll a backend twice with
different priorities without having to instantiate it twice.

We also differentiate between main backends and alternates; alternates have
lower priority and cannot be written to.

These changes come with some unit tests to make sure that the backend
sorting is consistent.

The libgit2 version has been bumped to 0.4.0.

This commit changes the external API:

CHANGED:
	struct git_odb_backend
		No longer has a `priority` attribute; priority for the backend
		in managed internally by the library.

	git_odb_add_backend(git_odb *odb, git_odb_backend *backend, int priority)
		Now takes an additional priority parameter, the priority that
		will be given to the backend.

ADDED:
	git_odb_add_alternate(git_odb *odb, git_odb_backend *backend, int priority)
		Add a backend as an alternate. Alternate backends have always
		lower priority than main backends, and writing is disabled on
		them.

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

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