profiles: Add 'package->manifest-entry'.

Suggested by Alex Kost <alezost@gmail.com>.

* guix/scripts/package.scm (options->installable)[package->manifest-entry]:
  Move to (guix profiles).
  [package->manifest-entry*]: New procedure.
  Use it.
* guix/profiles.scm (package->manifest-entry): New procedure.
* tests/profiles.scm (guile-for-build): New variable.
  Call '%guile-for-build'.
  ("profile-derivation"): New test.

1 files changed, 17 insertions, 0 deletions

diff --git a/guix/profiles.scm b/guix/profiles.scm
index 96c8ca0514..5e69e012f9 100644
--- a/guix/profiles.scm
+++ b/guix/profiles.scm
@@ -51,6 +51,7 @@
             manifest-matching-entries
 
             profile-manifest
+            package->manifest-entry
             profile-derivation
             generation-number
             generation-numbers
@@ -105,6 +106,22 @@
         (call-with-input-file file read-manifest)
         (manifest '()))))
 
+(define* (package->manifest-entry package #:optional output)
+  "Return a manifest entry for the OUTPUT of package PACKAGE.  When OUTPUT is
+omitted or #f, use the first output of PACKAGE."
+  (let ((deps (map (match-lambda
+                    ((label package)
+                     `(,package "out"))
+                    ((label package output)
+                     `(,package ,output)))
+                   (package-transitive-propagated-inputs package))))
+    (manifest-entry
+     (name (package-name package))
+     (version (package-version package))
+     (output (or output (car (package-outputs package))))
+     (item package)
+     (dependencies (delete-duplicates deps)))))
+
 (define (manifest->gexp manifest)
   "Return a representation of MANIFEST as a gexp."
   (define (entry->gexp entry)