This script can check most text file formats that we have checked our repositories, though it has some limitations. It ensures the entire licence appears on consecutive lines in the first comment in the file, and those lines contain nothing else.
The primary limitation of the checker is that each file suffix can only match one comment style, which is used for checking for the licence header. In text formats which accept multiple comment styles, there is now a canonical one that the licence must use. Where available, the licence should use a line comment style.
The other limitation is for files where the canonical style is block comments, like /* */, each line must be wrapped in the comment prefix and suffix, rather than the whole licence header being wrapped in a single comment prefix and suffix. This is an artefact of how the checker searches for the licence.
The checker is configured using a hjson file, which contains the exact licence header, and a list of file patterns to exclude from checking the licence for, which is used to exclude vendored and other externally sourced files.