can't thaw lsp-mode from fork/1

[RohanHart]

Running straight-thaw-versions fails on lsp-mode due to the change in 77f0521 as straight.el doesn't seem to be configured correctly when the fork/1 branch hasn't been fetched from the new remote. The *straight-process* buffers contains

$ git rev-parse --verify fork/1

fatal: Needed a single revision

Including the full remote name works, ie., git rev-parse --verify fork/fork/1