The existing detection logic was not working on any groff since at least
1.22.3 (November 2014), as could be seen by uncommenting the "$(info
...)" line. The regex used to match "nroff --version" output was
insufficiently flexible.
Fixes:
$ (cd doc && rm -f Guidebook && PATH=$HOME/groff-1.22.3/usr/bin:/bin make Guidebook) | grep NROFF
NROFFISGROFF=
$ (cd doc && rm -f Guidebook && PATH=$HOME/groff-1.22.4/usr/bin:/bin make Guidebook) | grep NROFF
NROFFISGROFF=
$ (cd doc && rm -f Guidebook && PATH=$HOME/groff-1.23.0/usr/bin:/bin make Guidebook) | grep NROFF
NROFFISGROFF=
$ (cd doc && rm -f Guidebook && PATH=$HOME/groff-HEAD/usr/bin:/bin make Guidebook) | grep NROFF
NROFFISGROFF=
Use a different approach in Make to recording groff detection. Use
"grep -c" (which is POSIX-conforming) to count the number of matches so
that we can use the contents of the Make macro `NROFFISGROFF` as a sort
of Boolean, which reads more idiomatically (in my opinion).
Further, instead of trying to lexically analyze a matched line in the
output of "nroff --version" and parse components of a version number out
of it, use GNU troff's built-in facility for extracting its minor
version number by storing the output of a tiny *roff document that
reports that datum (and nothing else).
Ignore warnings in category "scale" in any version of groff, because the
`tmac.n` macro package provokes them.
Clarify comments.
a8253dda00