Hi, What do you think?
(I'll send the output of 'git format-patch' when I implement the
command-line part.)
By the way, could you explain how the following works?
(match (scandir (dirname profile)
(cut regexp-exec %profile-rx <>)) ...)
How does 'regexp-exec' get its second argument? (I know how 'cut' works,
but I don't understand this particular snippet.)
Nikita
--- guix-package-orig 2012-12-16 17:38:40.000000000 +0000
+++ guix-package 2012-12-21 22:28:08.000000000 +0000
@@ -13,6 +13,7 @@
!#
;;; Guix --- Nix package management from Guile. -*- coding: utf-8 -*-
;;; Copyright (C) 2012 Ludovic Courtès <l...@gnu.org>
+;;; Copyright (C) 2012 Nikita Karetnikov <nik...@karetnikov.org>
;;;
;;; This file is part of Guix.
;;;
@@ -47,7 +48,8 @@
#:use-module (srfi srfi-37)
#:use-module (distro)
#:use-module (distro packages guile)
- #:export (guix-package))
+ #:export (guix-package)
+ #:export (roll-back))
(define %store
(open-connection))
@@ -87,13 +89,13 @@
(_
(error "unsupported manifest format" manifest))))
+(define (profile-rx profile)
+ (make-regexp (string-append "^" (regexp-quote (basename profile))
+ "-([0-9]+)")))
+
(define (latest-profile-number profile)
"Return the identifying number of the latest generation of PROFILE.
PROFILE is the name of the symlink to the current generation."
- (define %profile-rx
- (make-regexp (string-append "^" (regexp-quote (basename profile))
- "-([0-9]+)")))
-
(define* (scandir name #:optional (select? (const #t))
(entry<? (@ (ice-9 i18n) string-locale<?)))
;; XXX: Bug-fix version introduced in Guile v2.0.6-62-g139ce19.
@@ -129,7 +131,7 @@
(sort files entry<?))))
(match (scandir (dirname profile)
- (cut regexp-exec %profile-rx <>))
+ (cut regexp-exec (profile-rx profile) <>))
(#f ; no profile directory
0)
(() ; no profiles
@@ -137,7 +139,7 @@
((profiles ...) ; former profiles around
(let ((numbers (map (compose string->number
(cut match:substring <> 1)
- (cut regexp-exec %profile-rx <>))
+ (cut regexp-exec (profile-rx profile) <>))
profiles)))
(fold (lambda (number highest)
(if (> number highest)
@@ -177,6 +179,25 @@
packages)
#:modules '((guix build union))))
+(define (profile-number profile)
+ "Return PROFILE's number. PROFILE should be an absolute filename."
+ (match:substring (regexp-exec (profile-rx profile)
+ (basename (readlink profile))) 1))
+
+(define (roll-back)
+ "Roll back to the previous profile."
+ (let* ((current-profile-number
+ (string->number (profile-number %current-profile)))
+ (previous-profile
+ (string-append %current-profile "-"
+ (number->string (- current-profile-number 1))
+ "-link")))
+ (if (= current-profile-number 1)
+ (error "there are no other profiles.")
+ (delete-file %current-profile))
+
+ (symlink previous-profile %current-profile)))
+
;;;
;;; Command-line options.
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