This command, given a commit range commit1..commit2
, rewrites history so that git commit author becomes also git committer:
git filter-branch -f --commit-filter \
'export GIT_COMMITTER_NAME=\"$GIT_AUTHOR_NAME\";
export GIT_COMMITTER_EMAIL=\"$GIT_AUTHOR_EMAIL\";
export GIT_COMMITTER_DATE=\"$GIT_AUTHOR_DATE\";
git commit-tree $@' \
-- commit1..commit2