Failure to install using tarball

In principle, cabal supports a very convenient way of installing packages from tarballs. We should be able to reinstall copilot from the repos with the following call:

cabal install \
  https://github.com/Copilot-Language/copilot-c99/tarball/master \
  https://github.com/Copilot-Language/copilot-core/tarball/master \
  https://github.com/Copilot-Language/copilot-language/tarball/master \
  https://github.com/Copilot-Language/copilot-libraries/tarball/master \
  https://github.com/Copilot-Language/copilot-theorem/tarball/master \
  https://github.com/Copilot-Language/copilot/tarball/master

Currently, that does not work, because cabal expects the packages to be in a directory (in the tarball) whose name matches the version. For example, we are getting this message:

File in tar archive is not in the expected directory "copilot-core-3.0.1"

Because the file is in a directory with a name different from "copilot-core-3.0.1":

$ tar -zxvpf master.tar.gz 
x Copilot-Language-copilot-core-0186706/
x Copilot-Language-copilot-core-0186706/.gitignore
x Copilot-Language-copilot-core-0186706/.travis.yml
x Copilot-Language-copilot-core-0186706/LICENSE
x Copilot-Language-copilot-core-0186706/README.md
x Copilot-Language-copilot-core-0186706/Setup.hs
x Copilot-Language-copilot-core-0186706/copilot-core.cabal
x Copilot-Language-copilot-core-0186706/src/
x Copilot-Language-copilot-core-0186706/src/Copilot/
x Copilot-Language-copilot-core-0186706/src/Copilot/Core.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Error.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Expr.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/External.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Interpret.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Interpret/
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Interpret/Eval.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Interpret/Render.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Locals.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/MakeTags.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Operators.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/PrettyDot.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/PrettyPrint.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Spec.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/StructMarshal.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Array.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Dynamic.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Eq.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Equality.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Read.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Show.hs
x Copilot-Language-copilot-core-0186706/src/Copilot/Core/Type/Uninitialized.hs

This may be a bug in cabal, not in Copilot, but we can always transfer it if necessary. I'm using:

$ cabal --version
cabal-install version 2.4.1.0
compiled using version 2.4.1.0 of the Cabal library

on a Mac.

[fdedden]

I didn't know about this feature of cabal, and haven't used it before. It seems that cabal assumes a naming scheme, but Github doesn't deliver the tarball with the right directory names. I would assume cabal shouldn't need to care about the directory name, as it already has the tarball, but apparently things work different.

For this reason I think this is mostly a cabal issue.

[ivanperez-keera]

This is not a pressing issue, so it can just be discarded.