Add git_branch_delete rule

tests/rules/test_git_branch_delete.py

@@ -0,0 +1,22 @@
+import pytest
+from thefuck.rules.git_branch_delete import match, get_new_command
+from tests.utils import Command
+
+
+@pytest.fixture
+def stderr():
+    return '''error: The branch 'branch' is not fully merged.
+If you are sure you want to delete it, run 'git branch -D branch'.
+
+'''
+
+
+def test_match(stderr):
+    assert match(Command('git branch -d branch', stderr=stderr), None)
+    assert not match(Command('git branch -d branch'), None)
+    assert not match(Command('ls', stderr=stderr), None)
+
+
+def test_get_new_command(stderr):
+    assert get_new_command(Command('git branch -d branch', stderr=stderr), None)\
+        == "git branch -D branch"