Manual manual parsing

[Summertime]

It would be potentially better to grab the info from the manual pages directly instead of subproccing man, however we might still need to subproc man anyways to get paths

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Notes

1. man -w -> paths for man pages
   • works with man-db (fedora/debian/etc) and OpenBSD's implementation

[raylu]

for bonus points, implement man -w yourself. most of the logic is in guess_manpath: https://git.savannah.gnu.org/cgit/man-db.git/tree/src/manp.c#n665
you can see it in action via man -wd

[carlbordum]

Reimplementing 1400 lines of code of C to Python /can/ produce a short and beautiful program, but it is a lot of work and just a bit crazy. I would like to get rid of subprocess too. If anyone is crazy enough to attempt this, we also need to figure out how man differs on bsd...

[raylu]

you don't need to handle most of the cases (like when PATH is empty or unset). just

1. read /etc/manpath.config
2. build a PATH → MANPATH dict
3. search the PATH and pull out all the relevant MANPATHs
4. add the MANDATORY_MANPATHs
5. ignore BSD because who cares