Allow use of ArchiveCommand without depending on the jgit command-line
tools.

To avoid complicating the process of installing and upgrading JGit,
this does not add a dependency by the org.eclipse.jgit bundle on
commons-compress.  Instead, the caller is responsible for registering
any formats they want to use by calling ArchiveCommand.registerFormat.

This patch puts functionality that requires an archiver into a
separate org.eclipse.jgit.archive bundle for people who want it.  One
can use it by calling ArchiveCommand.registerFormat directly to
register its formats or by relying on OSGi class loading to load
org.eclipse.jgit.archive.FormatActivator, which takes care of
registration automatically.

Once the appropriate formats are registered, you can make a tar or zip
from a git tree object as follows:

	ArchiveCommand cmd = git.archive();
	try {
		cmd.setTree(tree).setFormat(fmt).setOutputStream(out).call();
	} finally {
		cmd.release();
	}

Change-Id: I418e7e7d76422dc6f010d0b3b624d7bec3b20c6e

Note the the settings are slightly less restrictive for test bundles.
-Also cleanup a couple of malformed javadocs
-Update compiler warnings/errors to include default values from Juno
-We now flag diagnosed null dereference as error. We didn't do that
 earlier because of some false positives.

Change-Id: I58386d63164e65d3d8d1998da3390d99bdc7381a
Signed-off-by: Chris Aniszczyk <zx@twitter.com>

This is a simple HTTP server that provides the minimum server side
support required for dumb (non-git aware) transport clients.

We produce the info/refs and objects/info/packs file on the fly
from the local repository state, but otherwise serve data as raw
files from the on-disk structure.

In the future we could better optimize the FileSender class and the
servlets that use it to take advantage of direct file to network
APIs in more advanced servlet containers like Jetty.

Our glue package borrows the idea of a micro embedded DSL from
Google Guice and uses it to configure a collection of Filters
and HttpServlets, all of which are matched against requests using
regular expressions.  If a subgroup exists in the pattern, it is
extracted and used for the path info component of the request.

Change-Id: Ia0f1a425d07d035e344ae54faf8aeb04763e7487
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Per CQ 3448 this is the initial contribution of the JGit project
to eclipse.org.  It is derived from the historical JGit repository
at commit 3a2dd9921c.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>