Cannot delete blob from tree

[Cloudate9]

Describe the bug While there is a way to create a tree (GHTreeBuilder) and to add an object to the tree (GHTreeBuilder#add), there is no clear way to remove an object (i.e. remove a file upon committing the tree + updating a ref). According to the GitHub REST api docs, one should be able to remove a file by passing in a null sha. This is not possible with GHTreeBuilder#add, as it requires a non-null content (not sha).

Is there something I'm missing here? Is that a separate method for this in the api? Note: GHRepository#getContent#delete will not suffice. That requires me to do a commit for every single file I want to delete, which is not ideal.

To Reproduce Steps to reproduce the behavior:

1. Create a new GHTreeBuilder, with a baseTree
2. Try to pass in a null value for content in GHTreeBuilder#add
3. Be sad at the compile errors

Expected behavior Upon committing the tree and updating a ref, the file with a null sha passed should be deleted.