kart diff between commits without working copy errors

[rcoup]

Describe the bug

kart diff errors in some situations without a working copy, even when the diff doesn't involve one.

To Reproduce

$ kart clone --no-checkout me@example.com/repo
$ kart diff -o json HEAD^1 HEAD
Error: Cannot generate working copy diff:
Repository has no working copy.
  (use "kart create-workingcopy")

Same occurs between any two commits/refs/trees, it's not related to HEAD specifically. Using A...B/A..B works fine, though produces different results (and .. doesn't work for trees)

Expected behaviour

Show the diff between two arbitrary commits/trees, which shouldn't relate to the working-copy.

Version Info

• OS: macOS 12.2.1
• Version: v0.11.4.dev0 @ 97ef458

[olsen232]

I think we only support COMMIT..COMMIT and COMMIT...COMMIT for specifying a commit range.
If you supply them as two args I think it parses it as COMMIT PATHSPEC.

But yeah we should support both for consistency with git - although git always supports so many weird things