The NAME section in manpages generally doesn't start with capital
letter (unless the word is 'proper noun') and doesn't end with
period. Notmuch manual pages now matches that "format".
- Replace references to section X below with page refences.
- Add SEE ALSO to each page. This is a bit error prone, because each
SEE ALSO section is different, i.e. a page does not refer to itself.
We mostly just cut and paste the command descriptions into individual
files, with a short header added to each one.
The splitting into subdirectories is to support the use of ./man as an
element in MANPATH, e.g. for testing.
