Add support for BUG_PREFIX in codereview.settings.

This change will allow projects other than chromium to specify 'BUG_PREFIX: project_name:' in their codereview.settings file.
Currently, the change is created with 'BUG=', entering a project's bug number there will point it to chromium's issue tracker. Adding a project specific prefix will make the links point to the project's issue tracker without the developer having to know about the magic prefix.

BUG=skia:1983

Review URL: https://codereview.chromium.org/132233006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@244801 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index d29dd38..1be5290 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -178,6 +178,7 @@
       ((['git', 'log', '--pretty=format:%s\n\n%b',
          'fake_ancestor_sha..HEAD'],),
        'desc\n'),
+      ((['git', 'config', 'rietveld.bug-prefix'],), ''),
     ]
 
   @classmethod
@@ -671,6 +672,8 @@
            'rietveld.tree-status-url'],), ''),
         ((['git', 'config', '--unset-all',
            'rietveld.viewvc-url'],), ''),
+        ((['git', 'config', '--unset-all',
+           'rietveld.bug-prefix'],), ''),
         ((['git', 'config', 'gerrit.host',
            'gerrit.chromium.org'],), ''),
         # DownloadHooks(False)
@@ -696,6 +699,8 @@
         ((['git', 'config', 'rietveld.viewvc-url'],), ''),
         (('ViewVC URL:',), ''),
         # DownloadHooks(True)
+        ((['git', 'config', 'rietveld.bug-prefix'],), ''),
+        (('Bug Prefix:',), ''),
         ((commit_msg_path, os.X_OK,), True),
         ]
     git_cl.main(['config'])