lint: Add '--load-path' option.

* guix/scripts/lint.scm (%options): Add '--load-path' option.
* doc/guix.texi: Document it.
* tests/guix-lint.sh: Test it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -9676,6 +9676,14 @@ and exit.
 Only enable the checkers specified in a comma-separated list using the
 names returned by @code{--list-checkers}.
 
+@item --load-path=@var{directory}
+@itemx -L @var{directory}
+Add @var{directory} to the front of the package module search path
+(@pxref{Package Modules}).
+
+This allows users to define their own packages and make them visible to
+the command-line tools.
+
 @end table
 
 @node Invoking guix size

guix/scripts/lint.scm

@@ -9,6 +9,7 @@
 ;;; Copyright © 2017 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;; Copyright © 2017, 2018 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2018, 2019 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2019 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -30,6 +31,7 @@
   #:use-module (guix lint)
   #:use-module (guix ui)
   #:use-module (guix scripts)
+  #:use-module (guix scripts build)
   #:use-module (gnu packages)
   #:use-module (ice-9 match)
   #:use-module (ice-9 format)
@@ -94,6 +96,9 @@ run the checkers on all packages.\n"))
   -c, --checkers=CHECKER1,CHECKER2...
                          only run the specified checkers"))
   (display (G_ "
+  -L, --load-path=DIR    prepend DIR to the package module search path"))
+  (newline)
+  (display (G_ "
   -h, --help             display this help and exit"))
   (display (G_ "
   -l, --list-checkers    display the list of available lint checkers"))
@@ -128,6 +133,9 @@ run the checkers on all packages.\n"))
                               %local-checkers
                               (alist-delete 'checkers
                                             result))))
+        (find (lambda (option)
+                (member "load-path" (option-names option)))
+              %standard-build-options)
         (option '(#\h "help") #f #f
                 (lambda args
                   (show-help)

tests/guix-lint.sh

@@ -76,3 +76,14 @@ then true; else false; fi
 
 # Make sure specifying multiple packages works.
 guix lint -c inputs-should-be-native dummy dummy@42 dummy
+
+
+# Use --load-path instead.
+unset GUIX_PACKAGE_PATH
+
+out=`guix lint -L $module_dir -c synopsis,description dummy 2>&1`
+if [ `grep_warning "$out"` -ne 3 ]
+then false; else true; fi
+
+# Make sure specifying multiple packages works.
+guix lint -L $module_dir -c inputs-should-be-native dummy dummy@42 dummy