machine: Add provenance tracking to each machine operating system.

* gnu/machine.scm (<machine>): Rename accessor to
'%machine-operating-system'.
(machine-operating-system): New procedure.
* doc/guix.texi (Service Reference): Mention it.

1 files changed, 6 insertions, 1 deletions

diff --git a/gnu/machine.scm b/gnu/machine.scm
index 05b03b21d49..b342fe21440 100644
--- a/gnu/machine.scm
+++ b/gnu/machine.scm
@@ -93,11 +93,16 @@
   make-machine
   machine?
   this-machine
-  (operating-system machine-operating-system) ; <operating-system>
+  (operating-system %machine-operating-system); <operating-system>
   (environment      machine-environment)      ; symbol
   (configuration    machine-configuration     ; configuration object
                     (default #f)))            ; specific to environment
 
+(define (machine-operating-system machine)
+  "Return the operating system of MACHINE."
+  (operating-system-with-provenance
+   (%machine-operating-system machine)))
+
 (define (machine-display-name machine)
   "Return the host-name identifying MACHINE."
   (operating-system-host-name (machine-operating-system machine)))