cuirass: add "--load-path" option

* bin/cuirass.in (%options): Add "--load-path" and "-L" command line options.
(show-help): Adapt.
* src/cuirass/base.scm (%load-package-path): New variable.
(preprend-to-package-module-path): New method.
(evaluate)[arguments]: Pass %load-package-path.
* bin/evaluate.in (main): Read new "load-package-path" argument and
add it to load lists with "preprend-to-package-module-path".

bin/cuirass.in

@@ -34,6 +34,7 @@ exec ${GUILE:-@GUILE@} --no-auto-compile -e main -s "$0" "$@"
 
       --one-shot            Evaluate and build jobs only once
       --cache-directory=DIR Use DIR for storing repository data
+  -L  --load-path=DIR       Prepend DIR to the package module search path.
   -S  --specifications=SPECFILE
                             Add specifications from SPECFILE to database.
   -D  --database=DB         Use DB to store build results.
@@ -48,6 +49,7 @@ exec ${GUILE:-@GUILE@} --no-auto-compile -e main -s "$0" "$@"
 (define %options
   '((one-shot                         (value #f))
     (cache-directory                  (value #t))
+    (load-path      (single-char #\L) (value #t))
     (specifications (single-char #\S) (value #t))
     (database       (single-char #\D) (value #t))
     (port           (single-char #\p) (value #t))
@@ -68,6 +70,7 @@ exec ${GUILE:-@GUILE@} --no-auto-compile -e main -s "$0" "$@"
          (%package-database (option-ref opts 'database (%package-database)))
          (%package-cachedir
           (option-ref opts 'cache-directory (%package-cachedir)))
+         (%load-package-path (option-ref opts 'load-path (%load-package-path)))
          (%use-substitutes? (option-ref opts 'use-substitutes #f)))
       (cond
        ((option-ref opts 'help #f)

bin/evaluate.in

@@ -32,7 +32,7 @@ exec ${GUILE:-@GUILE@} --no-auto-compile -e main -s "$0" "$@"
 
 (define* (main #:optional (args (command-line)))
   (match args
-    ((command load-path cachedir specstr database)
+    ((command load-path load-package-path cachedir specstr database)
      ;; Load FILE, a Scheme file that defines Hydra jobs.
      (let ((%user-module (make-fresh-user-module))
            (spec         (with-input-from-string specstr read))
@@ -58,6 +58,8 @@ exec ${GUILE:-@GUILE@} --no-auto-compile -e main -s "$0" "$@"
                  (exit 1)))
          (parameterize ((%package-database database)
                         (%use-substitutes? (assoc-ref spec #:use-substitutes?)))
+           (if load-package-path
+               (prepend-to-package-module-path load-package-path))
            ;; Call the entry point of FILE and print the resulting job sexp.
            (let* ((proc-name (assq-ref spec #:proc))
                   (proc    (module-ref %user-module proc-name))

src/cuirass/base.scm

@@ -22,6 +22,7 @@
   #:use-module (cuirass utils)
   #:use-module (guix derivations)
   #:use-module (guix store)
+  #:use-module (gnu packages)
   #:use-module (ice-9 format)
   #:use-module (ice-9 popen)
   #:use-module (ice-9 rdelim)
@@ -33,14 +34,20 @@
             evaluate
             build-packages
             process-specs
+            prepend-to-package-module-path
             ;; Parameters.
             %package-cachedir
+            %load-package-path
             %use-substitutes?))
 
 (define %use-substitutes?
   ;; Define whether to use substitutes
   (make-parameter #f))
 
+(define %load-package-path
+  ;; Extension of package module search path.
+  (make-parameter #f))
+
 (define %package-cachedir
   ;; Define to location of cache directory of this package.
   (make-parameter (or (getenv "CUIRASS_CACHEDIR")
@@ -52,6 +59,12 @@
           (scm-error 'wrong-type-arg
                      "%package-cachedir" "Not a string: ~S" (list #f) #f)))))
 
+(define (prepend-to-package-module-path load-path)
+  (%package-module-path (cons load-path (%package-module-path)))
+  (%patch-path (cons load-path (%patch-path)))
+  (set! %load-path (cons load-path %load-path))
+  (set! %load-compiled-path (cons load-path %load-compiled-path)))
+
 (define (call-with-time thunk kont)
   "Call THUNK and pass KONT the elapsed time followed by THUNK's return
 values."
@@ -114,6 +127,7 @@ if required."
                            (string-append (%package-cachedir) "/"
                                           (assq-ref spec #:name) "/"
                                           (assq-ref spec #:load-path))
+                           (%load-package-path)
                            (%package-cachedir)
                            (object->string spec)
                            (%package-database)))