If the user did not define header.Title when calling GenManTree(),
reset it after each call to GenMan(), otherwise the entire man page tree
would be stuck with the full command name that was calculated for the
first man page, leaving all subsequent man pages with an identical
but incorrect title.
This patch fixes the problem where lexgrog fails to parse the NAME section
when the provided command contains space, e.g. "rootcmd subcmd".
Explanation from Lintian:
Each manual page should start with a "NAME" section, which lists the
name and a brief description of the page separated by "\-". The "NAME"
section is parsed by lexgrog and used to generate a database that's
queried by commands like apropos and whatis. This tag indicates that
lexgrog was unable to parse the NAME section of this manual page.
For manual pages that document multiple programs, functions, files, or
other things, the part before "\-" should list each separated by a comma
and a space. Each thing listed must not contain spaces; a man page for a
two-part command like "fs listacl" must use something like "fs_listacl"
in the "NAME" section so that it can be parsed by lexgrog.
Ref: lexgrog(1), groff_man(7), groff_mdoc(7)
This slightly changes IsAvailableCommand in that a non-runnable command
with a runnable subcommand is now 'Available'
We also use IsAvailableCommand in the rest of the codebase instead of
half kinda sorta doing it incorrectly other places.
We previously had this weak argument called projectName which let you
set a single part of a man page header. Instead do the best we can if
the caller doesn't pass us anything, but let the caller specify anything
they want.
