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guix package: Add 'link-to-empty-profile'.

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* guix/scripts/package.scm (link-to-empty-profile): New function.
  (roll-back): Use it.
This commit is contained in:
Nikita Karetnikov 2013-09-25 03:34:49 +00:00
parent 4658b2c47b
commit 64d2e973fb
1 changed files with 11 additions and 7 deletions
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18
guix/scripts/package.scm
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@ -214,6 +214,15 @@ (define (generation-number profile)
(compose string->number (cut match:substring <> 1)))
0))
(define (link-to-empty-profile generation)
"Link GENERATION, a string, to the empty profile."
(let* ((drv (profile-derivation (%store) '()))
(prof (derivation->output-path drv "out")))
(when (not (build-derivations (%store) (list drv)))
(leave (_ "failed to build the empty profile~%")))
(switch-symlinks generation prof)))
(define (roll-back profile)
"Roll back to the previous generation of PROFILE."
(let* ((number (generation-number profile))
@ -236,13 +245,8 @@ (define (switch-link)
(_ "nothing to do: already at the empty profile~%")))
((or (zero? previous-number) ; going to emptiness
(not (file-exists? previous-generation)))
(let* ((drv (profile-derivation (%store) '()))
(prof (derivation->output-path drv "out")))
(when (not (build-derivations (%store) (list drv)))
(leave (_ "failed to build the empty profile~%")))
(switch-symlinks previous-generation prof)
(switch-link)))
(link-to-empty-profile previous-generation)
(switch-link))
(else (switch-link))))) ; anything else
(define (generation-time profile number)