DIY_GIT_in_Python/how_to/Change_13.md

• read-tree: Delete all existing stuff before reading

This is done so that we won’t have any old files left around after a read-tree.

Before this change, if we save tree A which contains only a.txt, then we save tree B which contains a.txt and b.txt and then we read-tree A, we will have b.txt left over in the working directory.