ArcanistMercurialAPI.getBlame seems to fail for files with trailing whitespace (like multiple newlines at the end of the file). I believe the problem is that it performs 'trim' on the blame output, which removes all trailing whitespace, then performs a regex check against each line with the following regex: /^\s*([^:]+?) [a-f0-9]{12}: (.*)$/ which expects a space after the final colon. This fails if the final line was empty, since the preceding space is trimmed as well.