How to generate a tree hash of a git sparse checkout?

Question

You can get the hash of a tree in a commit by doing:

git rev-parse 'HEAD^{tree}'

And you can get the hash of the tree in the index by doing:

git write-tree

However, in the case you did a sparse checkout by doing

git sparse-checkout init
git sparse-checkout set toto

Then running git write-tree will still print the hash of the full tree, including the files hidden by the sparse checkout. You can verify that by running git cat-file -p $(git write-tree), which will print all the files and directories at the top level.

How to generate the hash of a tree that includes only the files checked out by a sparse checkout?

Answer 1

I found one trick that works, although I don't know what the performance would look like in big repositories: you can git rm all the paths from the index, before doing git add with only the paths that are checked out.

# Remove all files, including the ones not checked out
git rm -r --sparse --cached --quiet .
# Re-add all checked-out files
git add -u
# Then run git write-tree to get a hash
git write-tree

• Joachim Sauer: I honestly think something like that is your only way, because git doesn't even have an internal tree object that's "cut down" to the sparse checkout until you create it, since it's only the checkout (i.e. the working directory) that's sparse and not anything else about the repo.