add git-split.sh

scripts/git-split.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+#
+# Copy a git file, keeping history.
+# Source: https://stackoverflow.com/a/53849613/3079831
+
+if (( $# != 2 )) ; then
+  echo "Usage: git-split.sh original copy"
+  exit 1
+fi
+
+from="$1"
+to="$2"
+branch="split-file"
+tmp="$from-temp-copy"
+
+git switch -c "$branch"
+git mv "$from" "$to"
+git commit -n -m "Split $from to $to - step 1"
+
+#REV=$(git rev-parse HEAD)
+git switch -
+
+git mv "$from" "$tmp"
+git commit -n -m "Split $from to $to - step 2"
+git merge "$branch"
+
+git commit -a -n -m "Split $from to $to - step 3"
+git mv "$tmp" "$from"
+git commit -n -m "Split file $from to $to - step 4"
+
+git branch -d "$branch"
+
+exit 0