Support .tool-versions

[klaaspieter]

asdf can automatically set current versions of tools by reading .tool-versions. Currently this does not work for asdf-xcode because changing Xcode versions works differently from what asdf expects.

asdf changes tool versions by placing shims in $PATH. For example when running ruby you're actually running ~/.asdf/shims/ruby which in turn looks up the current ruby version and invokes ~/.asdf/installs/ruby/[version]/bin/ruby for you.

With Xcode however we want to set DEVELOPER_DIR when entering a directory with a .tool-versions that specifies an Xcode version. Unfortunately asdf does not provide any hooks for this. As a matter of fact asdf doesn't even run when changing directories because it can always rely on it's shims to do the right thing.

This means we either:

1. Need to accept that managing versions is not possible
2. Find a way to make changing versions fit into asdf's shim system
3. Contribute a way to set DEVELOPER_DIR to asdf core

[airtonix]

Could we no "just" create ~/.asdf/installs/ruby/[version]/bin/xcode when we run asdf install xcode [version] which is a generated bash file that sets DEVELOPER_DIR ?

[klaaspieter]

@airtonix that's actually a brilliant suggestion. I don't know if it's going to work but it's worth a try!