No code intelligence on GitHub blame pages: "cannot determine file path"

Created by: lguychard

From Sentry: https://sentry.io/organizations/sourcegraph/issues/1264196822/events/b366f9d8f10546cdadc3ccf3777f3a48/

Example page: https://github.com/jenkinsci/ldapemail-plugin/blame/05051099ee9f56a530ca82d1ef5395c07026737d/src/main/java/com/mtvi/plateng/hudson/ldap/Configuration.java