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,
-and GIT_COMMITTER_DATE are set according to the current commit.
+and GIT_COMMITTER_DATE are set according to the current commit. If any
+evaluation of <command> returns a non-zero exit status, the whole operation
+will be aborted.
A 'map' function is available that takes an "original sha1 id" argument
and outputs a "rewritten sha1 id" if the commit has been already
--------------------------------------------------------------------------
git filter-branch --parent-filter \
- 'cat; test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>"' HEAD
+ 'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD
--------------------------------------------------------------------------
or even simpler: