Git filter-branch: possible to update commit messages to reference old commit IDs?
git
Solution
`--msg-filter` would be where to do it, and the original commit ID is in the environment variable `$GIT_COMMIT`, so (untested) make the message filter simply: `cat; echo "[COPIED FROM bob/helpers@$GIT_COMMIT]"`.
Problem
I can successfully run `git filter-branch` on some code to e.g. merge another repo into a subdirectory [1]: ``` git filter-branch --index-filter ' git ls-files -s | perl -pe "s{\t\"?}{$&helper/}" | GIT_INDEX_FILE=$GIT_INDEX_FILE.new git update-index --index-info && mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE ' remotes/helper/master ``` But now, I'd also love to expand each commit's message to include its former ID (SHA hash), since those commits may have had comments/conversation on GitHub which aren't getting transferred over. E.g. add an extra line like this (where `bob/helpers` is hardcoded/known in advance): ``` [COPIED FROM bob/helpers@76c7c080b3bd2f93dc78e4864899d668a57cd9f9] ``` As far as I can tell, Git's `msg-filter` only gives me the original message, and Git's `env-filter` doesn't contain the commit ID (SHA has) as an input variable. Is this possible then, or no? Thanks! [1] Via this great article, with the Perl filter from this email thread to workaround a bug on Mac OS X.