git remove trailing whitespace in new files before commit

Question

I know removing trailing whitespace can be done with a pre-commit hook. I am interested in doing it manually. I read the question here:
Make git automatically remove tra

Answer 1

I like Luke's answer, except for the limitation that you need to either manually specify the base commit, or use a rebase-style workflow, where your history is linearized. I propose a modification that doesn't need an extra argument and doesn't change the topology of your commit graph. As a shell command:

git rebase --whitespace=fix --onto $(git merge-base HEAD @{u})

Or as a ~/.gitconfig alias:

ws = "!git rebase --whitespace=fix --onto $(git merge-base HEAD @{u})"

I prefer this because sometimes I want to rebase my changes, but if I think think there might be a merge conflict I prefer to merge, so that both my original change and the conflict resolution will be recorded in the history. That way I can later second-guess the conflict resolution and redo it if necessary.

Given that I don't always rebase, I prefer not to mix whitespace-fixing with rebasing; hence this modification to Luke's answer.

In addition, I enable the default pre-commit hook which aborts on whitespace errors:

cp .git/hooks/pre-commit.sample .git/hooks/pre-commit

This gives the following workflow, which I like because it's manual enough that I know what's going on but automated enough not to get in the way:

1. hack hack hack, introduce whitespace error
2. attempt to commit
3. commit fails with whitespace error due to pre-commit hook
4. git commit --no-verify to commit anyway
5. git ws use the alias to fix

Note on the usage of --onto: It's not necessary here, but I find it easier to reason about how the rebase works this way. In Luke's version, HEAD~3 is the in the man page, while in my version keeps its default value of the real upstream of the branch. You wind up with the same result either way though.