If you want to change author’s and/or committer’s name and/or email in given GIT revisions, you can use the following script:
git filter-branch -f --commit-filter '
if [ "$GIT_AUTHOR_NAME" = "Old Author" ];
then
export GIT_AUTHOR_NAME = "New Author";
export GIT_AUTHOR_EMAIL = "[email protected]";
export GIT_COMMITTER_NAME = "New Author";
export GIT_COMMITTER_EMAIL = "[email protected]";
fi;
git commit-tree "$@"'
Now update the remote (bare) repository
git push --force --tags origin 'refs/heads/*'
I was facing task how to schedule an automatic backup/mirror of a website which allows connecting over FTP. PHP command exec was forbidden by the provider so it was not possible to run OS commands. PHP script execution time was set to quite short time so it was neither possible to zip using PHP functions and send the whole backup file somewhere easily. 
