Re: Display diffs between generations.

[Roel Janssen <roel@gnu.org>]

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From 7864ff2443f99fb227e90d0d176a977a30c88faa Mon Sep 17 00:00:00 2001
From: Roel Janssen <roel@gnu.org>
Date: Fri, 21 Oct 2016 11:31:52 +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 | 14 ++++++++++----
 guix/ui.scm              | 28 ++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index b87aee0..8b57f8d 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -667,24 +667,30 @@ 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)))
 
        (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)))
+              (for-each (cut list-generation
+                             display-profile-content-diff <>)
+                        (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))
+                     (unless (null-list? (cdr numbers))
+                       (for-each (cut list-generation
+                                      display-profile-content-diff <>)
+                                 (cdr numbers)))))))
              (else
               (leave (_ "invalid syntax: ~a~%")
                      pattern)))
diff --git a/guix/ui.scm b/guix/ui.scm
index eb85df3..4af8d52 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 +1071,33 @@ DURATION-RELATION with the current time."
           (format #t (_ "~a\t(current)~%") header)
           (format #t "~a~%" header)))))
 
+(define (display-profile-content-diff profile number)
+  "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)
+    (if (or (= old 0)
+            #f) ; Or first profile specified as an argument.
+        (display-profile-content profile new)
+        (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 (previous-generation-number profile number) number))
+
 (define (display-profile-content profile number)
   "Display the packages in PROFILE, generation NUMBER, in a human-readable
 way."
-- 
2.10.0


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Ludovic Courtès writes:

> Roel Janssen <roel@gnu.org> skribis:
>
>> Ludovic Courtès writes:
>
> [...]
>
>>> I think what I’m suggesting is that the first matching generation should
>>> be displayed in full using ‘display-profile-content’, and subsequent
>>> generations would be displayed as a diff.
>>>
>>> Thus, when viewing a single generation, as with --list-generations=42,
>>> we’d only display the full contents of that generation.
>>>
>>> Does that make sense?
>>
>> Ah, sorry, I forgot about this.  This makes sense.  But then, what should we
>> see when we do:
>>
>>   guix package --list-generations=42,46
>>
>> Should we see:
>>   Generation 42 ...:
>>   <full contents>
>>
>>   Generation 46 ...:
>>   <diff with 42>
>
> This one, IMO.

The attached patch implements this behavior.  However, because I use
@code{previous-generation-number} to determine which generation to diff
with, the following will not provide a diff as expected:

  guix package --list-generations=42,41,40

Any ideas on how to fix this?  Otherwise I'll give it another go over
the weekend.

Kind regards,
Roel Janssen