Since git-core ff5effd (v1.7.12.1) the native wire protocol transmits
the server and client implementation and version strings using
capability "agent=git/1.7.12.1" or similar.

Support this in JGit and hang the implementation data off UploadPack
and ReceivePack.  On HTTP transports default to the User-Agent HTTP
header until the client overrides this with the optional capability
string in the first line.

Extract the user agent string into a UserAgent class under transport
where it can be specified to a different value if the application's
build process has broken the Implementation-Version header in the
JGit package.

Change-Id: Icfc6524d84a787386d1786310b421b2f92ae9e65

Change-Id: I0a86ce0e393dfde9bb27f0b29e036e76c856396e
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Chris Aniszczyk <zx@twitter.com>

When a client POSTs to /git-{upload,receive}-pack, the first line
includes their client capabilities. As soon as the C git client sends
side-band(-64k), it goes into a state where it chokes on data not sent
in a valid sideband channel.

GitSmartHttpTools.sendError() is called early in the request, likely
before a {Upload,Receive}Pack handler is assigned or, even so, before it
has read the request. In some cases we must read the first line manually
within sendError() to tell whether sideband is needed.

Change-Id: I8277fd45a4ec3b71fa8f87404b4f5d1a09e0f384

This is intended to replace the RefFilter interface (but does not yet,
for backwards compatibility). That interface required lots of extra
scanning and copying in filter cases such as only advertising a subtree
of the refs directory. Instead, provide a hook that can be executed
right before ref advertisement, using the public methods on
UploadPack/ReceivePack to explicitly set the map of advertised refs.

Change-Id: I0067019a191c8148af2cfb71a675f2258c5af0ca

Embedding applications can use this hook to watch actions within
UploadPack and possibly reject them. This could be useful to prevent
clones of a large repository from this server, or to stop abusive
negotiation rounds that offer thousands of objects in a single batch.

Change-Id: Id96f1885ac4d61f22c80b6418fff54184b7348ba
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

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>