Use path based SHELL in Makefiles. It was suggested that this is a better solution for make for cases when there is no /usr/bin/env. See: https://github.com/purpleidea/mgmt/pull/694#discussion_r1015596204
This ports TestAstFunc2 from our home-grown content storage system to the txtar package. Since a single file can be used to represent the entire folder hierarchy, this makes it much easier to see and edit tests.