Install make.config with header files

[dschwoerer]

Installing into datadir causes issues as make.config contains many
settings and is thus not interchangable between different setups. If
the FHS [1] is used, different installations would conflict. This
has caused issues for fedora, where different MPI installations
share @datadir@.

[1] https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard

[ZedThree]

Did you mean to also remove the mpark variant stuff?

[dschwoerer]

Would you consider merging?

No, was an accident. Should be fixed now 👍

[ZedThree]

It's not clear to me that @includedir@ is definitely the correct place given that this isn't a header file, but as you point out, @datadir@ is supposed to be architecture-independent. I'm not suggesting we copy PETSc, but they put their equivalent files under lib/petsc/conf. CMake and pkg-config both install their files under @libdir@ for me.

The GNU installation standard suggests maybe @sysconfdir@, ${prefix}/etc? https://www.gnu.org/prep/standards/html_node/Directory-Variables.html

Also, I'm currently on a Fedora machine, and there's a /usr/lib64/openmpi/share directory -- is this not datadir? Is Fedora doing something other than setting prefix=/usr/lib64/openmpi?

I'm a bit less sure about this than I was initially. To install multiple versions of BOUT++, presumably you'd need to set prefix differently. Why then would they end up installing make.config in the same place?

I think this is likely fine, I'd just like to understand why it's necessary!

[dschwoerer]

Fedora is doing something different. For example header files are in /usr/include/openmpi-x86_64/bout++/
More documentation:
https://fedoraproject.org/wiki/Packaging:MPI#Packaging_of_MPI_compilers

We could use a different @datadir@, but that would result in duplicated .mo files, which isn't as nice. Also it violates the idea that datadir should be arch-independent. Some paths are arch-dependent, mostly due to multilib support.

@sysconfdir@ would avoid the conflict, but that would suggest the user can edit those files. However, this will most likely brake the installation, so I don't think that will work. @libdir@ might be better ...

[ZedThree]

@sysconfdir@ should be for read-only files according to that GNU document.

I don't have a strong opinion, as long as it works and is not obviously wrong.

[dschwoerer]

I think read-only refers to the program. This is basically /etc where the user/sysadmin can edit config files.