>From f920c91e0572539790952d9c28aec547d7bc0000 Mon Sep 17 00:00:00 2001
From: Benz Schenk <address@hidden>
Date: Fri, 21 Oct 2016 16:20:30 +0200
Subject: [PATCH] guix package: Display generation diffs.

* guix/ui.scm (display-profile-content-diff): New variable.
* guix/scripts/package.scm (process-query): Use display-profile-content-diff.

---
 guix/scripts/package.scm | 16 ++++++++++++----
 guix/ui.scm              | 30 ++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index b87aee0..8d148d7 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -667,24 +667,32 @@ processed, #f otherwise."
                      ((head tail ...) head))))
     (match (assoc-ref opts 'query)
       (('list-generations pattern)
-       (define (list-generation number)
+       (define (list-generation display-function number)
          (unless (zero? number)
            (display-generation profile number)
-           (display-profile-content profile number)
+           (display-function profile number)
            (newline)))
+       (define (diff-profiles profile numbers)
+         (unless (null-list? (cdr numbers))
+           (display-profile-content-diff profile (car numbers) (cadr numbers)))
+         (unless (null-list? (cdr numbers))
+           (diff-profiles profile (cdr numbers))))
 
        (cond ((not (file-exists? profile))      ; XXX: race condition
               (raise (condition (&profile-not-found-error
                                  (profile profile)))))
              ((string-null? pattern)
-              (for-each list-generation (profile-generations profile)))
+              (list-generation display-profile-content
+                               (car (profile-generations profile)))
+              (diff-profiles profile (profile-generations profile)))
              ((matching-generations pattern profile)
               =>
               (lambda (numbers)
                 (if (null-list? numbers)
                     (exit 1)
                     (leave-on-EPIPE
-                     (for-each list-generation numbers)))))
+                     (list-generation display-profile-content (car numbers))
+                     (diff-profiles profile numbers)))))
              (else
               (leave (_ "invalid syntax: ~a~%")
                      pattern)))
diff --git a/guix/ui.scm b/guix/ui.scm
index eb85df3..c93b44f 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -87,6 +87,7 @@
             matching-generations
             display-generation
             display-profile-content
+            display-profile-content-diff
             roll-back*
             switch-to-generation*
             delete-generation*
@@ -1070,6 +1071,35 @@ DURATION-RELATION with the current time."
           (format #t (_ "~a\t(current)~%") header)
           (format #t "~a~%" header)))))
 
+(define (display-profile-content-diff profile number1 number2)
+  "Display the changed packages in PROFILE compared to generation NUMBER."
+
+  (define (equal-entry? first second)
+    (string= (manifest-entry-item first) (manifest-entry-item second)))
+
+  (define (display-entry entry prefix)
+    (match entry
+      (($ <manifest-entry> name version output location _)
+       (format #t " ~a ~a\t~a\t~a\t~a~%" prefix name version output location))))
+
+  (define (list-entries number)
+    (manifest-entries (profile-manifest (generation-file-name profile number))))
+
+  (define (display-diff profile old new)
+    (format #t (_ "Generation ~a\t~a ~%") new
+                          (date->string
+                           (time-utc->date
+                            (generation-time profile new))
+                           "~b ~d ~Y ~T"))
+    (let ((added (lset-difference
+                  equal-entry? (list-entries new) (list-entries old)))
+          (removed (lset-difference
+                    equal-entry? (list-entries old) (list-entries new))))
+      (for-each (cut display-entry <> "+") added)
+      (for-each (cut display-entry <> "-") removed)))
+
+  (display-diff profile number1 number2))
+
 (define (display-profile-content profile number)
   "Display the packages in PROFILE, generation NUMBER, in a human-readable
 way."
-- 
2.10.1