Replace pywikibot.showDiff with patched version

Pywikibot.bot.userPut does not support setting the value of diff context
so it is always zero. Therefore we need to patch either userPut or
showDiff to get some context.

Related Task: [https://fs.golderweb.de/index.php?do=details&task_id=113 FS#113]

bots/markpages.py

@@ -28,8 +28,10 @@ with templates
 
 from datetime import datetime
 
+import pywikibot
 from pywikibot import pagegenerators
 from pywikibot.bot import CurrentPageBot
+from pywikibot.diff import PatchManager
 
 import mwparserfromhell as mwparser
 
@@ -280,6 +282,10 @@ class MarkPagesBot( CurrentPageBot ):  # sets 'current_page' on each treat()
         @param kwargs: Additional parameters directly given to L{Bot.userPut}.
         @type kwargs: dict
         """
+
+        # Monkey patch pywikibot.showDiff
+        pywikibot.showDiff = showDiff
+
         if ignore_save_related_errors is None:
             ignore_save_related_errors = self.ignore_save_related_errors
         if ignore_server_errors is None:
@@ -289,3 +295,15 @@ class MarkPagesBot( CurrentPageBot ):  # sets 'current_page' on each treat()
             ignore_save_related_errors=ignore_save_related_errors,
             ignore_server_errors=ignore_server_errors,
             **kwargs)
+
+
+# We need to have a patched version to set context param to value greater 0 as
+# pywikibot.bot.userPut() currently does not support this value
+def showDiff(oldtext, newtext, context=3):
+    """
+    Output a string showing the differences between oldtext and newtext.
+
+    The differences are highlighted (only on compatible systems) to show which
+    changes were made.
+    """
+    PatchManager(oldtext, newtext, context=context).print_hunks()