Stack: Document how to install specific versions of stack

[sjakobi]

I want to pin the version of stack I'm using in a CI script (AppVeyor). I was looking for instructions on installing specific versions in https://docs.haskellstack.org/en/stable/install_and_upgrade/ but didn't find any.

For now I went with downloading https://github.com/commercialhaskell/stack/releases/download/v2.1.3/stack-2.1.3-windows-x86_64.zip, but I'm not sure whether that's the recommended way.

[mattaudesse]

Yep, I believe most people either use a static link like you've done or incorporate some environment variables to adjust the version portions of their URI.

Any interest in submitting a docs PR?

[Fyrbll]

I haven't been involved in this discussion, but I'm interested in this as a possible first contribution to stack.

Based on the comments up to now, I'm thinking of adding a sub-section called "Install older versions" to the install and upgrade guide.

The sub-section will say:
"To install a specific version of stack, navigate to the desired version on the GitHub release page, and click the appropriate link under its Assets drop-down menu.

Alternatively, use the URL https://github.com/commercialhaskell/stack/releases/download/vVERSION/stack-VERSION-PLATFORM.EXTENSION
For example, if the tarball for stack 2.1.0.1, osx-x86_64 is at https://github.com/commercialhaskell/stack/releases/download/v2.1.0.1/stack-2.1.0.1-osx-x86_64.tar.gz"

Does this look okay?

[sjakobi]

That seems like a good start! :)

I think a snippet that people can just copy into their appveyor.yml would be very helpful. Feel free to use dhall's appveyor.yml for inspiration.