get-developers: add option to get developers for files

get-developers: add option to get developers for files

The DEVELOPERS file lists file patterns, but the get-developers script
only supports getting packages and CPU architectures. Some files are
neither of those, e.g. defconfigs, support files, package infras, ...

Add a '-f' option that allows to give a list of files for which to get
the developer(s).

Note that the DEVELOPERS file contains directories as well as files,
and the directories are not expanded into individual files. Therefore,
we have to use f.startswith(devfile) to match a directory. This assumes
that the directory name ends with /, otherwise 'package/python' would
also match 'package/python-foo'. Since we make sure that directories do
end with / in the DEVELOPERS file, and since false positives are not
much of an issue in this case, this isn't a problem.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>