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