I was especially delighted to see the “+ NEW BUILD” button. However it seems to be broken on my installation, it just gives me the error message: “Unable to start new build: Not Found”. Apparently the code tries to POST to /api/repos/<repo/path>/builds which returns a 404.
I just tested the feature and was unable to reproduce. A 404 not found could indicate the named branch was not found, or it could indicate no .drone.yml exists at the specified branch. You might consider checking your drone logs (with debug mode enabled) for more details.
I did some further debugging. Calling the api with a commit specified works as expected but it doesn’t work without or with specifying a (existing) branch.