[MacPorts] #63080: base: "port lint stack" breaks on port 2.7.99

[MacPorts]

#63080: base: "port lint stack" breaks on port 2.7.99
-----------------------+----------------------
 Reporter:  snowflake  |      Owner:  jmroot
     Type:  defect     |     Status:  assigned
 Priority:  Normal     |  Milestone:
Component:  base       |    Version:  2.7.99
 Keywords:             |       Port:
-----------------------+----------------------
 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 at 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.

-- 
Ticket URL: <https://trac.macports.org/ticket/63080>
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