Use --repository_url to override the git origin URL

This patch allows the user to override the current git repository's origin URL
by setting --repository_url.

We use this where I work with a custom ReviewBoard/Github:FI integration. We
have canonical repos in Github that contributors fork. Contributors work in
their fork while a script on the ReviewBoard server clones the canonical repo
and adds a remote/fetches commits for every fork so that ReviewBoard has access
to all commits.

The repository URL that our integration needs in order to use post-review is the
canonical repo, and not the fork. --repository-url seems like a reasonable entry
point to add this functionality.

In use in our organization by our engineering group.

Reviewed at http://reviews.reviewboard.org/r/2376/

rbtools/postreview.py

@@ -2813,11 +2813,17 @@ def get_repository_info(self):
         if remote and remote != '.' and merge:
             self.upstream_branch = '%s/%s' % (remote, merge)
 
-        self.upstream_branch, origin_url = self.get_origin(self.upstream_branch,
-                                                           True)
+        url = None
+        if options.repository_url:
+            url = options.repository_url
+        else:
+            self.upstream_branch, origin_url = \
+                self.get_origin(self.upstream_branch, True)
+
+            if not origin_url or origin_url.startswith("fatal:"):
+                self.upstream_branch, origin_url = self.get_origin()
 
-        if not origin_url or origin_url.startswith("fatal:"):
-            self.upstream_branch, origin_url = self.get_origin()
+            url = origin_url.rstrip('/')
 
         # Central bare repositories don't have origin URLs.
         # We return git_dir instead and hope for the best.
@@ -3785,7 +3791,9 @@ def parse_options(args):
                            "outside of a working copy (currently only "
                            "supported by Subversion with --revision-range or "
                            "--diff-filename and ClearCase with relative "
-                           "paths outside the view)")
+                           "paths outside the view). For git, this specifies"
+                           "the origin url of the current repository, "
+                           "overriding the origin url supplied by the git client.")
     parser.add_option("-d", "--debug",
                       action="store_true", dest="debug", default=DEBUG,
                       help="display debug output")