Merge pull request #230 from scorphus/git-diff-staged-rule

add(rule): add the new git_diff_staged rule

thefuck/rules/git_diff_staged.py

@@ -0,0 +1,6 @@
+def match(command, settings):
+    return command.script.startswith('git d')
+
+
+def get_new_command(command, settings):
+    return '{} --staged'.format(command.script)