Have a Conda backend

[certik]

This is related to #69 but it's a separate issue. fpm should be able to create a Conda package for the project, so that it's easy to submit it to conda-forge.

[everythingfunctional]

What's required for a Conda package?

[certik]

Here is a Conda package for my dftatom Fortran package:

https://github.com/conda-forge/dftatom-feedstock/

The main config file:

https://github.com/conda-forge/dftatom-feedstock/blob/5f4e97e3c089337b5a8e4c9be6c2c7f36dca8c6c/recipe/meta.yaml

Linux / macOS build script:

https://github.com/conda-forge/dftatom-feedstock/blob/5f4e97e3c089337b5a8e4c9be6c2c7f36dca8c6c/recipe/build.sh

And Windows build script:

https://github.com/conda-forge/dftatom-feedstock/blob/5f4e97e3c089337b5a8e4c9be6c2c7f36dca8c6c/recipe/bld.bat

All of which could be generated. The build process could simply just call fpm on all platforms.

[everythingfunctional]

That seems like it wouldn't actually require any changes to FPM.

[certik]

One still has to generate things like "description", "name" (both of which fpm knows), and the proper template to call fpm. But yes, it should be a simple backend to fpm.

[awvwgk]

Now that we have a fpm version at conda-forge, packaging fpm projects is quite straight-forward except for some minor issues. Is there anything further required on the fpm side?

[certik]

Do we have some example of a Conda package that uses fpm?

I think there is a number of issues:

• Dependencies must be packaged as Conda
• Alternatively, they should be pre-downloaded.
• They should not be downloading during the build (as the currently do)

The same issue will happen when packaging for Debian and other distros. They like to have a clean upstream tarball, and then no downloads happening during the build. So we need to improve fpm to be able to provide that, one way or another.