--- /dev/null
+#!/bin/sh
+set -e
+rm -rf ../d
+git checkout for-gitk-upstream
+git format-patch --subject-prefix='PATCH GITK' --cover-letter \
+ -o ../d remotes/gitk/master
+count=$(ls -1 ../d | wc -l)
+
+rename 's/$/-A/' ../d/0000-*
+
+git checkout for-git-upstream
+git format-patch -n --start-number=$(($count)) --cover-letter \
+ -o ../d remotes/upstream/master
+
+rename 's/$/-B/' ../d/0000-*
+
+count=$(ls -1 ../d | wc -l)
+count=$(($count-1))
+
+cat ../d/0000-*-[AB] >../d/0000-cover-letter.txt
+rm ../d/0000-*-[AB]
+
+cp ../play/0000-gitk-cover-letter.txt ../d/0000-cover-letter.txt
+
+for f in ../d/*; do
+ perl -i -pe '
+ next if m/^$/..0;
+ next unless m/^Subject/;
+ s{(PATCH(?: \w+)? \d+/)\d+(?=\])}{${1}'"$count"'};
+ ' $f
+done