[PATCH b4 4/4] Distribute the manpage with the pip package

[Philippe Blain <levraiphilippeblain@gmail.com>]

The 'data_files' option to setuptools.setup can be used to install
additional files "outside" of the package [1].

Use it so that the manpage is installed with the package.

Install the manpage to '$PREFIX/share/man/man5', mimicking what the
Filesystem Hiararchy Standard mandates for the '/usr/local/' prefix [2].

Prefer '$PREFIX/share/man/man5' to '$PREFIX/man/man5' since the later is
deprecated [3].

[1] https://docs.python.org/3/distutils/setupscript.html#installing-additional-files
[2] https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s11.html#idm236091648080
[3] https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s11.html#ftn.idm236091648080

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
---

Notes:
    A small note: by installing the man page to '$PREFIX/share/man', we are
    unfortunately trusting every other package installed in '$PREFIX' to follow
    the same convention.
    
    The reason is that when invoking `man <cmd>`, man(1) looks for the <cmd> man
    page by searching for man directories "near" the directory where <cmd> is found
    in 'PATH'. This search is limited to a single "nearby" directory and at least
    for some versions of man on some Linux distributions [1], '$PREFIX/man' is
    preferred to '$PREFIX/share/man'.
    
    So if manpages exist in both locations, man will only look in '$PREFIX/man' and
    our manpage won't be found. The behavior of man(1) on macOS is the opposite;
    the search prefers '$PREFIX/share/man' to '$PREFIX/man' [2].
    
    We could install the man page at both locations, but then we are wasting disk
    space (does it matter?). We can't easily use a symlink from one location to the
    other one, because this is not well supported by pip/setuptools [3].
    
    [1] https://github.com/conda-forge/git-feedstock/pull/65#discussion_r322762265
    [2] https://github.com/conda-forge/git-feedstock/issues/66#issuecomment-539095424
    [3] https://github.com/pypa/pip/issues/5856

 setup.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/setup.py b/setup.py
index 65ede59..867b5cf 100644
--- a/setup.py
+++ b/setup.py
@@ -38,6 +38,7 @@ setup(
     license='GPLv2+',
     long_description=read('man/b4.5.rst'),
     long_description_content_type='text/x-rst',
+    data_files = [('share/man/man5', ['man/b4.5'])],
     keywords=['git', 'lore.kernel.org', 'patches'],
     install_requires=[
         'requests'
-- 
2.27.0