Re: doc: Give users the freedom to use their own style in the HTML documentation

[Jose E. Marchesi]

Hi Bruno.
    
    I always prefer to read documentation in HTML format. When reading the poke
    documentation,
    
    1) I was annoyed to have a white-text-on-black-background style, because it
       hurts the eyes in an otherwise black-text-on-white-background desktop.
    
    2) I was even surprised to see that the doc I generate locally, as well as
       the doc a user can generate from the distributed tarballs [1], makes a
       network reference to www.jemarch.net when viewed for the first time.
       It gives the owner of that site (and every internet node operator on
       the way) the opportunity to get a notification when the user opens the
       documentation for the first time.
    
    In fact, the AM_MAKEINFOHTMLFLAGS variable is not overridable by the user
    (who can only give a MAKEINFOFLAGS as a 'configure' argument).
    
    I would propose to give users
      - the default style by default,
      - the freedom to use their own style instead of yours.
    
    Patch attached.

Yep, I agree.
OK for master.
Thanks!

    Bruno
    
    [1] 
https://gitlab.com/gnu-poke/ci-distcheck/-/jobs/artifacts/master/raw/poke-snapshot.tar?job=check-optimized
    
    >From c876a1cf41db09bce28ea2037d2cb0c4f99fc67d Mon Sep 17 00:00:00 2001
    From: Bruno Haible <bruno@clisp.org>
    Date: Sat, 6 Jun 2020 21:09:01 +0200
    Subject: [PATCH] doc: Give users the freedom to use their own style in the
     HTML documentation.
    
    * doc/Makefile.am (AM_MAKEINFOHTMLFLAGS): Remove variable.
    * HACKING (Building): Explain how to set a custom style in the HTML
    documentation.
    ---
     HACKING         | 11 ++++++++++-
     doc/Makefile.am |  2 --
     2 files changed, 10 insertions(+), 3 deletions(-)
    
    diff --git a/HACKING b/HACKING
    index b657794..cde9d0f 100644
    --- a/HACKING
    +++ b/HACKING
    @@ -373,7 +373,16 @@ Then, you can run ``configure``::
     
       $ mkdir build/ && cd build
       $ ../configure
    -  
    +
    +Here, you can give as arguments to 'configure'
    +  - configure options, as listen in the 'configure --help' output,
    +  - Makefile variable assignments for building the binaries, as
    +    described in the INSTALL file,
    +  - Makefile variable assignments for building the documentation,
    +    for example
    +      MAKEINFOFLAGS="--css-ref=http://www.jemarch.net/homepage.css";
    +    to get HTML documentation styled like the "Applied Pokology" blog.
    +
     Finally::
     
       $ make
    diff --git a/doc/Makefile.am b/doc/Makefile.am
    index c915da8..bca7a93 100644
    --- a/doc/Makefile.am
    +++ b/doc/Makefile.am
    @@ -51,8 +51,6 @@ pkgdata_DATA = nodelist
     #   like a bug, since the "Footnotes" heading is <h4> itself.  Using a
     #   header for this is ugly anyway.
     
    -AM_MAKEINFOHTMLFLAGS = --css-ref='http://www.jemarch.net/homepage.css'
    -
     html-local:
        sed -i -e '/^<h2.*contents-heading.*/,/<a name="Top">.*/d' \
                    -e 's/^<h1.*settitle.*//' \