Add nightly creating an old version of core

It creates the old version of core (7 days ago).
In case the current version fails badly

Bug: https://phabricator.wikimedia.org/T98592

nightly

@@ -30,13 +30,31 @@ git rev-parse --short HEAD >> pywikibot/version
 git gc --aggressive --prune=all --quiet
 cd scripts/i18n
 git gc --aggressive --prune=all --quiet
+#Create an old version of core. Bug T98592
+cd /data/project/pywikibot/public_html/
+rm -rf /data/project/pywikibot/public_html/core_old
+git clone https://gerrit.wikimedia.org/r/pywikibot/core.git core_old
+cd /data/project/pywikibot/public_html/core_old/externals
+rm -rf httplib2
+git clone https://gerrit.wikimedia.org/r/pywikibot/externals/httplib2.git
+cd /data/project/pywikibot/public_html/core_old/scripts
+rm -rf i18n
+git clone https://gerrit.wikimedia.org/r/pywikibot/i18n.git
+cd /data/project/pywikibot/public_html/core_old
+git checkout $(git rev-list -n 1 --before=`date --date="7 days ago" +%F` master) -b core_old
+git gc --aggressive --prune=all --quiet
+#End
 rm /data/project/pywikibot/public_html/core.zip
+rm /data/project/pywikibot/public_html/core_old.zip
 rm /data/project/pywikibot/public_html/compat.zip
 rm /data/project/pywikibot/public_html/core.tar.gz
 rm /data/project/pywikibot/public_html/compat.tar.gz
+rm /data/project/pywikibot/public_html/core_old.gz
 cd /data/project/pywikibot/public_html/
 zip -9 -r -q core.zip core
+zip -9 -r -q core_old.zip core_old
 zip -9 -r -q compat.zip compat
 tar czPf core.tar.gz core/
+tar czPf core_old.tar.gz core_old/
 tar czPf compat.tar.gz compat/