Reviewing upstream packages to write debian/copyright files is tedious but important manual work. It is done during initial packaging and after every new upstream release.

Making initial copyright file construction and subsequent review/update easier will improve Debian's software quality.

Starting with Stretch (Debian 9) there are significantly improved tools over previous releases to help.

Note that some of the tools listed here are run by check-all-the-things -f copyright.

cme update dpkg-copyright

licensecheck --copyright -r `find * -type f` | \
  /usr/lib/cdbs/licensecheck2dep5 > debian/copyright.auto

See also