[BUG] File diffs do not work with Gluon/partial workspaces

[mikeseese]

Describe the bug
The file diffs do not work at all for partial/Gluon workspaces. This is due to cm status returning a -1 changeset when on branch. The fix should be to use cm fileinfo on each file request rather than getting a changeset for the whole workspace.

To Reproduce
Steps to reproduce the behavior:

1. Create partial workspace with Gluon
2. Make a change to a text-based file
3. Try to see change in VSCode

Expected behavior
File diffs should work for both partial and full workspaces.

Screenshots

Relevant output
Any text that appears in the Plastic SCM output in VS Code that could be helpful to troubleshoot.

Environment (please complete the following information):

• OS: Windows 11
• Extension version: 0.1.2
• Visual Studio Code version 1.72.2

Additional context
I'm working on implementing a fix