+\f
+;;;
+;;; Provenance tracking.
+;;;
+
+(define (object->pretty-string obj)
+ "Like 'object->string', but using 'pretty-print'."
+ (call-with-output-string
+ (lambda (port)
+ (pretty-print obj port))))
+
+(define (channel->code channel)
+ "Return code to build CHANNEL, ready to be dropped in a 'channels.scm'
+file."
+ `(channel (name ',(channel-name channel))
+ (url ,(channel-url channel))
+ (branch ,(channel-branch channel))
+ (commit ,(channel-commit channel))))
+
+(define (channel->sexp channel)
+ "Return an sexp describing CHANNEL. The sexp is _not_ code and is meant to
+be parsed by tools; it's potentially more future-proof than code."
+ `(channel (name ,(channel-name channel))
+ (url ,(channel-url channel))
+ (branch ,(channel-branch channel))
+ (commit ,(channel-commit channel))))
+
+(define (provenance-file channels config-file)
+ "Return a 'provenance' file describing CHANNELS, a list of channels, and
+CONFIG-FILE, which can be either #f or a <local-file> containing the OS
+configuration being used."
+ (scheme-file "provenance"
+ #~(provenance
+ (version 0)
+ (channels #+@(if channels
+ (map channel->sexp channels)
+ '()))
+ (configuration-file #+config-file))))
+
+(define (provenance-entry config-file)
+ "Return system entries describing the operating system provenance: the
+channels in use and CONFIG-FILE, if it is true."
+ (define profile
+ (current-profile))
+
+ (define channels
+ (and=> profile profile-channels))
+
+ (mbegin %store-monad
+ (let ((config-file (cond ((string? config-file)
+ (local-file config-file "configuration.scm"))
+ ((not config-file)
+ #f)
+ (else
+ config-file))))
+ (return `(("provenance" ,(provenance-file channels config-file))
+ ,@(if channels
+ `(("channels.scm"
+ ,(plain-file "channels.scm"
+ (object->pretty-string
+ `(list
+ ,@(map channel->code channels))))))
+ '())
+ ,@(if config-file
+ `(("configuration.scm" ,config-file))
+ '()))))))
+
+(define provenance-service-type
+ (service-type (name 'provenance)
+ (extensions
+ (list (service-extension system-service-type
+ provenance-entry)))
+ (default-value #f) ;the OS config file
+ (description
+ "Store provenance information about the system in the system
+itself: the channels used when building the system, and its configuration
+file, when available.")))
+
+\f
+;;;
+;;; Cleanup.
+;;;
+