54bd94ad24
The only time we should call SetSelectedLineIdx is when we are happy for a select range to be retained which means things like moving the selected line index to top top/bottom or up/down a page as the user navigates. But in every other case we should now call SetSelection because that will set the selected index and cancel the range which is almost always what we want.
FileTree Package
This package handles the representation of file trees. There are two ways to render files: one is to render them flat, so something like this:
dir1/file1
dir1/file2
file3
And the other is to render them as a tree
dir1/
file1
file2
file3
Internally we represent each of the above as a tree, but with the flat approach there's just a single root node and every path is a direct child of that root. Viewing in 'tree' mode (as opposed to 'flat' mode) allows for collapsing and expanding directories, and lets you perform actions on directories e.g. staging a whole directory. But it takes up more vertical space and sometimes you just want to have a flat view where you can go flick through your files one by one to see the diff.
This package is not concerned about rendering the tree: only representing its internal state.