How can I checkout an untracked file in a git stash?

Question

Assume I have stashed some changes using one of:

git stash -u
git stash --include-untracked

I can checkout an individual file from the stash via

git checkout stash@{0} -- filename

That works if git knows about "filename", but doesn't work if "filename" is untracked. Is there any way to checkout untracked files from a stash?

Answer 1

git stash internally creates special black magic merge commits to store different parts of your changes. The merge commit has the original base commit (what you had at the top of the branch when you stashed) as its first parent, a throwaway commit representing the index contents at time of stashing as its second parent, and (only if you used --include-untracked) a throwaway commit containing the untracked files as its third parent.

So, the merge commit references the untracked files (as one of its parents)... but it doesn't actually include those files in its own tree (if that doesn't make any sense, either you've got a few things to learn yet about Git's internals... or you know too much about merge commits and this whole construct just seems too horrible to think about ;)).

In short... to access the untracked parts of your stash, access its third parent: git checkout stash@{0}^3 -- filename