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

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

doc/guix.texi

@@ -70,6 +70,7 @@ Copyright @copyright{} 2019 Kyle Andrews@*
 Copyright @copyright{} 2019 Alex Griffin@*
 Copyright @copyright{} 2019 Guillaume Le Vaillant@*
 Copyright @copyright{} 2020 Leo Prikler@*
+Copyright @copyright{} 2019 Simon Tournier@*
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -10038,6 +10039,14 @@ Display the graph for @var{system}---e.g., @code{i686-linux}.
 
 The package dependency graph is largely architecture-independent, but there
 are some architecture-dependent bits that this option allows you to visualize.
+
+@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
 
 On top of that, @command{guix graph} supports all the usual package

guix/scripts/graph.scm

@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2019 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -35,6 +36,7 @@
   #:use-module ((guix scripts build)
                 #:select (show-transformation-options-help
                           options->transformation
+                          %standard-build-options
                           %transformation-options))
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
@@ -473,6 +475,9 @@ package modules, while attempting to retain user package modules."
                  (lambda (opt name arg result)
                    (alist-cons 'system arg
                                (alist-delete 'system result eq?))))
+         (find (lambda (option)
+                (member "load-path" (option-names option)))
+              %standard-build-options)
          (option '(#\h "help") #f #f
                  (lambda args
                    (show-help)
@@ -501,6 +506,9 @@ Emit a representation of the dependency graph of PACKAGE...\n"))
   (display (G_ "
   -s, --system=SYSTEM    consider the graph for SYSTEM--e.g., \"i686-linux\""))
   (newline)
+  (display (G_ "
+  -L, --load-path=DIR    prepend DIR to the package module search path"))
+  (newline)
   (show-transformation-options-help)
   (newline)
   (display (G_ "

tests/guix-graph.sh

@@ -1,5 +1,6 @@
 # GNU Guix --- Functional package management for GNU
 # Copyright © 2015, 2016, 2019 Ludovic Courtès <ludo@gnu.org>
+# Copyright © 2019 Simon Tournier <zimon.toutoune@gmail.com>
 #
 # This file is part of GNU Guix.
 #
@@ -20,10 +21,29 @@
 # Test the 'guix graph' command-line utility.
 #
 
-tmpfile1="t-guix-graph1-$$"
-tmpfile2="t-guix-graph2-$$"
+module_dir="t-guix-graph-$$"
+mkdir "$module_dir"
+trap "rm -rf $module_dir" EXIT
+
+tmpfile1="$module_dir/t-guix-graph1-$$"
+tmpfile2="$module_dir/t-guix-graph2-$$"
 trap 'rm -f "$tmpfile1" "$tmpfile2"' EXIT
 
+
+cat > "$module_dir/foo.scm"<<EOF
+(define-module (foo)
+  #:use-module (guix packages)
+  #:use-module (gnu packages base))
+
+(define-public dummy
+  (package (inherit hello)
+    (name "dummy")
+    (version "42")
+    (synopsis "dummy package")
+    (description "dummy package. Only used for testing purposes.")))
+EOF
+
+
 guix graph --version
 
 for package in guile-bootstrap coreutils python
@@ -59,3 +79,6 @@ guix graph git | grep 'label = "openssl'
 guix graph git --with-input=openssl=libressl | grep 'label = "libressl'
 if guix graph git --with-input=openssl=libressl | grep 'label = "openssl'
 then false; else true; fi
+
+# Try --load-path
+guix graph -L $module_dir dummy | grep 'label = "dummy'