Add git_fix_author script.

nix/configuration/roles/base/files/git_fix_author.bash

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+#
+set -euo pipefail
+IFS=$'\n\t'
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+
+git filter-branch --env-filter '
+WRONG_EMAIL="old@email.foo"
+NEW_NAME="New Name"
+NEW_EMAIL="new@email.bar"
+
+if [ "$GIT_COMMITTER_EMAIL" = "$WRONG_EMAIL" ]
+then
+    export GIT_COMMITTER_NAME="$NEW_NAME"
+    export GIT_COMMITTER_EMAIL="$NEW_EMAIL"
+fi
+if [ "$GIT_AUTHOR_EMAIL" = "$WRONG_EMAIL" ]
+then
+    export GIT_AUTHOR_NAME="$NEW_NAME"
+    export GIT_AUTHOR_EMAIL="$NEW_EMAIL"
+fi
+' --tag-name-filter cat --commit-filter 'git commit-tree -S "$@";' -- --branches --tags