Add git_pull rule

thefuck/rules/git_pull.py

@@ -0,0 +1,12 @@
+def match(command, settings):
+    return ('git' in command.script
+            and 'pull' in command.script
+            and 'set-upstream' in command.stderr)
+
+
+def get_new_command(command, settings):
+    line = command.stderr.split('\n')[-3].strip()
+    branch = line.split(' ')[-1]
+    set_upstream = line.replace('<remote>', 'origin')\
+                       .replace('<branch>', branch)
+    return u'{} && {}'.format(set_upstream, command.script)