How can I undo parts of the last commit, while selecting which parts using an interactive patch mode? This would come in useful when you've accidentally checked in a few lines too many in your last commit, e.g. debug print statements or whitespace changes that your editor did for you.
The naive approach is
git commit --amend --interactive --patch
but this does not seem to work. i.e. it just drops you into an editor to do a rewording.
The ugly approach is
git show HEAD~1:path/to/some/file > path/to-some/file
git add -up
git commit --amend
but this is annoying because it makes you specify the file beforehand, and makes you re-add all patches one by one (rather than allowing you to un-add only bits and pieces)
What about
git reset -p HEAD~
git commit --amend --no-edit
First command will allow you to unstage chunks interactively (select y for the parts you want to get out of the commit), then the commit amend will write that into the new commit.