Add conditional expressions of the form:
foo := if lhs == rhs { then } else { otherwise }
`lhs`, `rhs`, `then`, and `otherwise` are all arbitrary expressions, and
can recursively include other conditionals. Conditionals short-circuit,
so the branch not taken isn't evaluated.
It is also possible to test for inequality with `==`.
The `--choose` subcommand runs a chooser to select a recipe to run. The
chooser should read lines containing recipe names from standard input,
and write one of those names to standard output.
The chooser defaults to `fzf`, a popular fuzzy finder, but can be
overridden by setting $JUST_CHOOSER or passing `--chooser <CHOOSER>`.
Combine all integration test binaries into a single binary with the root
in `tests/lib.rs`. This also turns of automatic test discovery, so
when adding another set of integration tests, a mod statement will need
to be added to `tests/lib.rs`.
