To catch all SHA256 hashes from a template, even the ones which
are used only under certain preconditions, use grep [0-9a-f]{64} to
find all hashes in a template.
The may be some false positives which does not hurt the intended
purpose to purge obsolete distfiles.
Signed-off-by: Jürgen Buchmüller <pullmoll@t-online.de>
When sourcing templates to get $checksum there are templates
calling msg_error(). This is not relevant for this function,
thus define a local dummy msg_error() to ignore these cases.
