Without the change checks issue the fllowing warning:
$ nix flake check
trace: warning: The option `nix.useSandbox' defined in `makeTest parameters' has been renamed to `nix.settings.sandbox'.
trace: warning: The option `nix.useSandbox' defined in `makeTest parameters' has been renamed to `nix.settings.sandbox'.
trace: warning: The option `nix.maxJobs' defined in `makeTest parameters' has been renamed to `nix.settings.max-jobs'.
...
nixos/nix#6290 introduced a regex pattern to account for tags when
resolving sourcehut refs. nixos/nix#4638 reafactored the code,
accidentally treating the pattern as a regular string, causing all
non-HEAD ref resolving to break.
This fixes the regression and adds more test cases to avoid future
breakage.
The new implementation relies on tab separting the hash and ref (this is how sourcehut does it). This fixes the integration test to use a tab instead of a space.
