If you have to change an old commit message over multiple branches (i.e., the commit with the erroneous message is present in multiple branches) you might want to use:
git filter-branch -f --msg-filter \
'sed "s///g"' -- --all
Git will create a temporary directory for rewriting and additionally backup old references in refs/original/.
-f will enforce the execution of the operation. This is necessary if the temporary directory is already present or if there are already references stored under refs/original. If that is not the case, you can drop this flag.
-- separates filter-branch options from revision options.
--all will make sure that all branches and tags are rewritten.
Due to the backup of your old references, you can easily go back to the state before executing the command.
Say, you want to recover your master and access it in branch old_master:
git checkout -b old_master refs/original/refs/heads/master
