Require branch deletion permission for pushes over HTTP

Since smart HTTP can perform a branch deletion over HTTP requests, we
need to disambiguate web requests from the web UI from HTTP requests
coming from a git client tool such as git push.  Moving all git
commands into the AccessPath.GIT category and making a different
category for the web UI allows us to tell these apart, so we can
correctly require delete branch permission when removing a branch
through a git command.

This is a safety feature to prevent project owners from accidentally
creating or deleting branches over git push, even though they can do
this through the web UI without additional access controls.

Bug: issue 393
Change-Id: I14cc68e31f5263913f5d9715a8f2241b5766bf23
Signed-off-by: Shawn O. Pearce <sop@google.com>
Reviewed-by: Nico Sallembien <nsallembien@google.com>

gerrit-sshd/src/main/java/com/google/gerrit/sshd/SuExec.java

@@ -114,7 +114,7 @@ public final class SuExec extends BaseCommand {
     }
 
     return new SshSession(session.get(), peer, userFactory.create(
-        AccessPath.SSH, new Provider<SocketAddress>() {
+        AccessPath.SSH_COMMAND, new Provider<SocketAddress>() {
           @Override
           public SocketAddress get() {
             return peer;