Remove manual --tbr support and convert it into automatic TBR= detection.

tests/tbr.sh

-#!/bin/bash
-
-# Tests the "tbr" functionality, which lets you submit without uploading
-# first.
-
-set -e
-
-. ./test-lib.sh
-
-setup_initsvn
-setup_gitsvn
-
-(
-  set -e
-  cd git-svn
-
-  # We need a server set up, but we don't use it.
-  git config rietveld.server localhost:1
-
-  echo "some work done" >> test
-  git add test; git commit -q -m "work"
-
-  test_expect_success "git-cl dcommit tbr without an issue" \
-    "$GIT_CL dcommit -f --tbr -m 'foo-quux'"
-
-  git svn -q rebase >/dev/null 2>&1
-  test_expect_success "dcommitted code has proper description" \
-      "git show | grep -q 'foo-quux'"
-
-  test_expect_success "upstream svn has our commit" \
-      "svn log $REPO_URL 2>/dev/null | grep -q 'foo-quux'"
-)
-SUCCESS=$?
-
-cleanup
-
-if [ $SUCCESS == 0 ]; then
-  echo PASS
-fi