~~~~~~~
The filters are applied in the order as listed below. The <command>
-argument is always evaluated in shell using the 'eval' command.
+argument is always evaluated in shell using the 'eval' command (with the
+notable exception of the commit filter, for technical reasons).
Prior to that, the $GIT_COMMIT environment variable will be set to contain
the id of the commit being rewritten. Also, GIT_AUTHOR_NAME,
GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL,