guix: home: Add list-generations.

Julien LepillerThu Sep 19 22:50:49+0200 2019

0936fbc

guix: home: Add list-generations. * guix/scripts/home.scm: Support list-generations command.

guix/scripts/home.scm

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   reconfigure      switch to or create a new home configuration\n"))
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  (display (G_ "\
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   build            build the home configuration without installing anything\n"))
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  (display (G_ "\
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   list-generations list the home generations\n"))
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  (show-build-options-help)
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  (display (G_ "
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  -h, --help             display this help and exit"))

…

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              (rename-file %home data-directory)))
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          (symlink %current-home %home)))))
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(define (list-generations pattern)
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  "Display in a human-readable format all the home generations matching
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PATTERN, a string.  When PATTERN is #f, display all the home generations."
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  (cond ((not (file-exists? %current-home))             ; XXX: race condition
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	 (raise (condition (&profile-not-found-error
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			     (profile %current-home)))))
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	((not pattern)
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	 (for-each (lambda (number) (display-generation %current-home number)) (profile-generations %current-home)))
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	((matching-generations pattern %current-home)
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	 =>
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	 (lambda (numbers)
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	   (if (null-list? numbers)
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	       (exit 1)
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	       (leave-on-EPIPE
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		 (for-each (lambda (number) (display-generation %current-home number)) numbers)))))))
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;;;
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;;; Entry point.
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;;;
…
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  (case command
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    ;; The following commands do not need to use the store, and they do not need
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    ;; an operating system configuration file.
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    ((list-generations)
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     (let ((pattern (match args
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			   (() #f)
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			   ((pattern) pattern)
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			   (x (leave (G_ "wrong number of arguments~%"))))))
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       (list-generations pattern)))
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    ;; The following commands need to use the store, but they do not need an
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    ;; operating system configuration file.
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    ;; The following commands need to use the store, and they also
…
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        (alist-cons 'argument arg result)
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        (let ((action (string->symbol arg)))
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          (case action
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            ((build reconfigure)
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            ((build reconfigure list-generations)
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             (alist-cons 'action action result))
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            (else (leave (G_ "~a: unknown action~%") action))))))
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