How can I easily fixup a past commit?

Question

I just read amending a single file in a past commit in git but unfortunately the accepted solution \'reorders\' the commits, which is not what I want. So here\'s my question

Answer 1

A bit late to the party, but here is a solution that works as the author imagined.

Add this to your .gitconfig:

[alias]
    fixup = "!sh -c '(git diff-files --quiet || (echo Unstaged changes, please commit or stash with --keep-index; exit 1)) && COMMIT=$(git rev-parse $1) && git commit --fixup=$COMMIT && git rebase -i --autosquash $COMMIT~1' -"

Example usage:

git add -p
git fixup HEAD~5

However if you have unstaged changes, you must stash them before the rebase.

git add -p
git stash --keep-index
git fixup HEAD~5
git stash pop

You could modify the alias to stash automatically, instead of giving a warning. However, if the fixup does not apply cleanly you will need pop the stash manually after fixing the conflicts. Doing both the saving and popping manually seems more consistent and less confusing.