Fix ruby Portfile

[Korusuke]

Fixes #36

[reneeotten]

thanks @Korusuke the changes in the template look good and work as expected!

I just had another look at the error message [ERROR ] [Backend] Could not determine the type of the source archive that you now successfully suppress, but on second thought there shouldn't be a need for that.

@Steap added Archive to upt-rubygems and the frontend indeed correctly returns an archive. I think that there is a bug in the get_archive function in upt itself. If you add some print statements and run upt package -f rubygems -b macports treetop then you'll see the following:

self.archives = [<upt.upt.Archive object at 0x106664c50>]
archive.archive_type = ArchiveType.RUBYGEM

which seems all correct. However, archive_type in this function is still archive_type = ArchiveType.SOURCE_TARGZ and that means that it's filtered out in lines 187-188.

[Korusuke]

Yes, agree even I think that it should be fixed in upt as get_archive() sets the archive type as targz2 by default.
As of now I have changed the code so it makes a exception while calling the function and not in error as that is more appropriate this way but I still think that this should be handled by upt.

[reneeotten]

I guess my choice words using "bug" is probably too strong / wrong, it might actually be a feature ;) In all cases except for upt-rubygems the SOURCE_TARGZ is the correct type, so it makes sense that this is the default. So perhaps your change to only call the _get_archive function with specifying the RUBYGEM archive type is the correct thing to do, I am not sure whether upt can take care of this automagically - lets see what @Steap has to say.

[Steap]

What you could do here is define an "archive_type" class attribute for all subclasses of MacPortsPackage (just like the "template" attribute) that would be equal to "upt.ArchiveType.RUBYGEM" or "upt.ArchiveType.SOURCE_TARGZ" (note that the latter does not necessarily refer to a tar.gz, because I fucked up when naming it :p).

You would then write:

archive_name = self.upt_pkg.get_archive(self.archive_type).filename

[Steap]

lets see what @Steap has to say.

Yep, you're right. get_archive() defaults to looking for a source archive, because that is the most common use case, but one may want to look for a Python wheel, a Ruby gem, etc.

[reneeotten]

thanks @Korusuke I am happy with this, it works exactly as intended now! @Steap if you agree, please do merge this PR or approve the changes and I'll get to it tomorrow.

[Steap]

@reneeotten It seems OK, but I'll let you merge, you understand these Ruby/Macports issues better than me :)