base: "port lint stack" breaks on port 2.7.99

[snowflake (Dave Evans)]

I have built the port command both on the current git master as of yesterday and also on this checkout:

commit 994ae759bed50d4fc89189910a4f0574d81b93bb (HEAD)
Author: Joshua Root <jmr@macports.org>
Date:   2021-05-19 08:05:25 +0100

    Bump version on master to 2.7.99

If I try port lint stack in any random directory, it returns

port lint stack
Error: Port stack not found

If I cd to the directory containing stack's Portfile and try port lint it returns:

port lint 
Can't map the URL 'file://.' to a port description file ("can't read "configure.env": can't read "haskell_stack.env": can't read "haskell_stack.yaml": can't read "worksrcpath": can't read "worksrcdir": can't read "distname": can't read "name": no such variable").
Please verify that the directory and portfile syntax are correct.
To use the current port, you must be in a port's directory.

Trying other commands such as clean and install in the stack directory also show similar breakage.

[jmroot (Joshua Root)]

#63076