On history react, when the initial screen has been loaded, no default pathname is selected. This PR adds logic for selecting default pathname and getting the diff for that pathname.
Also, add some other small changes, the notable ones are:
- Refactor some type naming and file structure related to the history file tree
- Refactor file tree selectable hooks (merge selectable context provider into the main provider)
- prevent clicking on the same file tree item by checking the current pathname before invoking the handler function
GitOrigin-RevId: 73c36e9ed918ae3d92dd47108fbe8542a7571bdd
