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-server/src/main/java/com/google/gerrit/server/AccessPath.java

@@ -19,11 +19,14 @@ public enum AccessPath {
   /** An unknown access path, probably should not be special. */
   UNKNOWN,
 
-  /** Access through the web interface. */
-  WEB,
+  /** Access through the web UI. */
+  WEB_UI,
 
-  /** Access through an SSH command, e.g. git fetch or push. */
-  SSH,
+  /** Access through an SSH command that is not invoked by Git. */
+  SSH_COMMAND,
+
+  /** Access from a Git client using any Git protocol. */
+  GIT,
 
   /** Access through replication */
   REPLICATION;