git-reset-committer-date-rebase-head

#!/usr/bin/env bash
#
# During a rebase, the committer date gets set to the current date (after the first modified
# commit). This script can be invoked by a script passed to `git rebase -x <script>`, to reset
# the current commit's committer date to match that of the original commit being applied.

rebase_head="$(git rebase-head)"
if [ -z "$rebase_head" ]; then
    echo "No rebase detected (.git/REBASE_HEAD missing, no relevant SHA recognized in .git/rebase-merge/done)" >&2
    exit 1
fi

git set-committer-date "$rebase_head"