filter-branch works only after running it twice
git, git-filter-branch
Solution
Presumably the ones showing up after the first `filter-branch` were named via `refs/original/refs/heads/master` and the like. `--all` means all references underneath `refs/`. Remember that `filter-branch` saves (backs up, as it were) the original references under `refs/original/` (or any other name space you define with `--original`). You can use those to put things back if the filter-branch operation made a mess.
With `-f` (force), `filter-branch` will run even if there's already a backup branch name-space: it removes the old backup to make room for a new one. Without `-f` it instead does this:
die "Cannot create a new backup.
A previous backup already exists in $orig_namespace
Force overwriting the backup with -f"
By removing the backup, the second `filter-branch` operation deleted all the `refs/original/` entries — something you are normally supposed to do manually once you're happy with the result of the filter. In this case, since the re-application of the filter harmlessly did nothing, the second `filter-branch` took care of the cleanup for you.
Problem
To remove build results from our repository, I ran `git filter-branch -f --index-filter 'git rm --cached --ignore-unmatch */obj/*' -- --all`. It appeared to work. Oddly, running `git log --oneline --name-only --all -- */obj/*` displayed a list of commits that still contain the `obj` directory. So, I ran `filter-branch` a second time. Git told me: ``` Rewrite d57c56e00f713854d8b5889a259e10bd9be6a83c (316/316) WARNING: Ref 'refs/heads/master' is unchanged WARNING: Ref 'refs/remotes/origin/master' is unchanged WARNING: Ref 'refs/remotes/origin/carousel' is unchanged WARNING: Ref 'refs/remotes/origin/master' is unchanged ``` Now when I again run the `log` command, the history is empty. The `obj` directory is no longer in the history. That's good, of course, but the question remains: Why did I need to run the `filter-branch` twice?