Ludovic Courtès (2014-10-06 23:27 +0400) wrote:
> Alex Kost <alez...@gmail.com> skribis:
>
>> A patch is attached. Some comments:
>>
>> - ‘shitted-generation’ is not a very good name, I think. Ideas?
>
> ‘shifted-generation’ is better :-), but otherwise maybe
> ‘relative-generation’? No strong opinion.
I like ‘relative-generation’, thanks.
>> - ‘previous-generation-number’ may use ‘shifted-generation’ now:
>>
>> (define* (previous-generation-number profile #:optional
>> (number (generation-number profile)))
>> "Return the number of the generation before generation NUMBER of
>> PROFILE, or 0 if none exists. It could be NUMBER - 1, but it's not the
>> case when generations have been deleted (there are \"holes\")."
>> (or (shifted-generation profile -1 number)
>> 0))
>>
>> Worth changing?
>
> Yes, why not.
Done.
>> - Perhaps it would be better to make 2 commits (?): one for adding
>> ‘shifted-generation’ and ‘switch-to-generation’ procedures to (guix
>> profiles) and another is for adding the “--switch-generation” option
>> itself.
>
> Yes.
Done.
>> - Also I made a couple of cosmetic changes in “guix/scripts/package.scm”:
>> * ‘filter-map’ was replaced by 'for-each' because it was called only for
>> side effects there;
>> * ‘begin’ was removed from ‘cond’.
>> I think these changes do not deserve a separate commit and may stay in
>> this patch. Is it OK?
>
> Several patches make it easier to reason about the changes, but it’s OK
> here. Your call.
OK, thanks, I left those changes.
>> From 3cc52d1aade5e9723c38c0af5fa4437cbdf1a9b6 Mon Sep 17 00:00:00 2001
>> From: Alex Kost <alez...@gmail.com>
>> Date: Mon, 6 Oct 2014 17:35:51 +0400
>> Subject: [PATCH] guix package: Add '--switch-generation' option.
>>
>> * doc/guix.texi (Invoking guix package): Update documentation.
>> * guix/profiles.scm (shifted-generation, switch-to-generation): New
>> procedures.
>> * guix/scripts/package.scm: Add '--switch-generation' option.
>> (switch-to-previous-generation): Use 'switch-to-generation'.
>
> Could you add a test in tests/guix-package.sh?
>
> The rest looks good to me, thanks for working on it!
Thanks, I've added a couple of tests. The new patches are attached.
Further improvements (documentation may be unsatisfactory)?
>From 9493421a4e094be6686ff6f28749946d491f81cd Mon Sep 17 00:00:00 2001
From: Alex Kost <alez...@gmail.com>
Date: Tue, 7 Oct 2014 11:50:44 +0400
Subject: [PATCH 1/2] profiles: Add procedures for switching generations.
* guix/scripts/package.scm (switch-to-previous-generation): Move to...
* guix/profiles.scm: ... here. Use 'switch-to-generation'.
(relative-generation): New procedure.
(previous-generation-number): Use it.
(switch-to-generation): New procedure.
---
guix/profiles.scm | 53 ++++++++++++++++++++++++++++++++++++++++--------
guix/scripts/package.scm | 9 --------
2 files changed, 45 insertions(+), 17 deletions(-)
diff --git a/guix/profiles.scm b/guix/profiles.scm
index 18733a6..9920881 100644
--- a/guix/profiles.scm
+++ b/guix/profiles.scm
@@ -71,9 +71,12 @@
generation-number
generation-numbers
profile-generations
+ relative-generation
previous-generation-number
generation-time
- generation-file-name))
+ generation-file-name
+ switch-to-generation
+ switch-to-previous-generation))
;;; Commentary:
;;;
@@ -569,16 +572,28 @@ former profiles were found."
'()
generations)))
-(define (previous-generation-number profile number)
+(define* (relative-generation profile shift #:optional
+ (current (generation-number profile)))
+ "Return PROFILE's generation shifted from the CURRENT generation by SHIFT.
+SHIFT is a positive or negative number.
+Return #f if there is no such generation."
+ (let* ((abs-shift (abs shift))
+ (numbers (profile-generations profile))
+ (from-current (memq current
+ (if (negative? shift)
+ (reverse numbers)
+ numbers))))
+ (and from-current
+ (< abs-shift (length from-current))
+ (list-ref from-current abs-shift))))
+
+(define* (previous-generation-number profile #:optional
+ (number (generation-number profile)))
"Return the number of the generation before generation NUMBER of
PROFILE, or 0 if none exists. It could be NUMBER - 1, but it's not the
case when generations have been deleted (there are \"holes\")."
- (fold (lambda (candidate highest)
- (if (and (< candidate number) (> candidate highest))
- candidate
- highest))
- 0
- (generation-numbers profile)))
+ (or (relative-generation profile -1 number)
+ 0))
(define (generation-file-name profile generation)
"Return the file name for PROFILE's GENERATION."
@@ -589,4 +604,26 @@ case when generations have been deleted (there are \"holes\")."
(make-time time-utc 0
(stat:ctime (stat (generation-file-name profile number)))))
+(define (switch-to-generation profile number)
+ "Atomically switch PROFILE to the generation NUMBER."
+ (let ((current (generation-number profile))
+ (file (generation-file-name profile number)))
+ (cond ((not (file-exists? profile))
+ (format (current-error-port)
+ (_ "profile '~a' does not exist~%")
+ profile))
+ ((not (file-exists? file))
+ (format (current-error-port)
+ (_ "generation ~a does not exist~%")
+ number))
+ (else
+ (format #t (_ "switching from generation ~a to ~a~%")
+ current number)
+ (switch-symlinks profile file)))))
+
+(define (switch-to-previous-generation profile)
+ "Atomically switch PROFILE to the previous generation."
+ (switch-to-generation profile
+ (previous-generation-number profile)))
+
;;; profiles.scm ends here
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index fc9c37b..d0f1458 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -94,15 +94,6 @@ return PROFILE unchanged. The goal is to treat '-p ~/.guix-profile' as if
(switch-symlinks generation prof)))
-(define (switch-to-previous-generation profile)
- "Atomically switch PROFILE to the previous generation."
- (let* ((number (generation-number profile))
- (previous-number (previous-generation-number profile number))
- (previous-generation (generation-file-name profile previous-number)))
- (format #t (_ "switching from generation ~a to ~a~%")
- number previous-number)
- (switch-symlinks profile previous-generation)))
-
(define (roll-back store profile)
"Roll back to the previous generation of PROFILE."
(let* ((number (generation-number profile))
--
2.1.2
>From 0d89e5466741d8f80a1ac27502cb6cd600afb796 Mon Sep 17 00:00:00 2001
From: Alex Kost <alez...@gmail.com>
Date: Tue, 7 Oct 2014 12:05:06 +0400
Subject: [PATCH 2/2] guix package: Add '--switch-generation' option.
* guix/scripts/package.scm: Add '--switch-generation' option.
(guix-package): Adjust accordingly.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Invoking guix package): Document it.
---
doc/guix.texi | 15 +++++++++++++++
guix/scripts/package.scm | 35 ++++++++++++++++++++++++++++++-----
tests/guix-package.sh | 14 +++++++++++++-
3 files changed, 58 insertions(+), 6 deletions(-)
diff --git a/doc/guix.texi b/doc/guix.texi
index f6357bd..c6921b1 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -784,6 +784,21 @@ Installing, removing, or upgrading packages from a generation that has
been rolled back to overwrites previous future generations. Thus, the
history of a profile's generations is always linear.
+@item --switch-generation=@var{pattern}
+@itemx -S @var{pattern}
+Switch to a particular generation defined by @var{pattern}.
+
+@var{pattern} may be either a generation number or a number prefixed
+with ``+'' or ``-''. The latter means: move forward/backward by a
+specified number of generations. For example, if you want to return to
+the latest generation after @code{--roll-back}, use
+@code{--switch-generation=+1}.
+
+The difference between @code{--roll-back} and
+@code{--switch-generation=-1} is that @code{--switch-generation} will
+not make a zeroth generation, so if a specified generation does not
+exist, the current generation will not be changed.
+
@item --search-paths
@cindex search paths
Report environment variable definitions, in Bash syntax, that may be
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index d0f1458..4a4417e 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -400,6 +400,9 @@ Install, remove, or upgrade PACKAGES in a single transaction.\n"))
-d, --delete-generations[=PATTERN]
delete generations matching PATTERN"))
(display (_ "
+ -S, --switch-generation=PATTERN
+ switch to a generation matching PATTERN"))
+ (display (_ "
-p, --profile=PROFILE use PROFILE instead of the user's default profile"))
(newline)
(display (_ "
@@ -479,6 +482,10 @@ Install, remove, or upgrade PACKAGES in a single transaction.\n"))
(values (alist-cons 'delete-generations (or arg "")
result)
#f)))
+ (option '(#\S "switch-generation") #t #f
+ (lambda (opt name arg result arg-handler)
+ (values (alist-cons 'switch-generation arg result)
+ #f)))
(option '("search-paths") #f #f
(lambda (opt name arg result arg-handler)
(values (cons `(query search-paths) result)
@@ -704,13 +711,31 @@ more information.~%"))
(generation-number profile))
;; First roll back if asked to.
- (cond ((and (assoc-ref opts 'roll-back?) (not dry-run?))
- (begin
- (roll-back (%store) profile)
- (process-actions (alist-delete 'roll-back? opts))))
+ (cond ((and (assoc-ref opts 'roll-back?)
+ (not dry-run?))
+ (roll-back (%store) profile)
+ (process-actions (alist-delete 'roll-back? opts)))
+ ((and (assoc-ref opts 'switch-generation)
+ (not dry-run?))
+ (for-each
+ (match-lambda
+ (('switch-generation . pattern)
+ (let* ((number (string->number pattern))
+ (number (and number
+ (case (string-ref pattern 0)
+ ((#\+ #\-)
+ (relative-generation profile number))
+ (else number)))))
+ (if number
+ (switch-to-generation profile number)
+ (format (current-error-port)
+ "Cannot switch to generation '~a'~%" pattern)))
+ (process-actions (alist-delete 'switch-generation opts)))
+ (_ #f))
+ opts))
((and (assoc-ref opts 'delete-generations)
(not dry-run?))
- (filter-map
+ (for-each
(match-lambda
(('delete-generations . pattern)
(cond ((not (file-exists? profile)) ; XXX: race condition
diff --git a/tests/guix-package.sh b/tests/guix-package.sh
index 9b0e75e..5ad0873 100644
--- a/tests/guix-package.sh
+++ b/tests/guix-package.sh
@@ -100,6 +100,16 @@ then
test "`readlink_base "$profile"`" = "$profile-1-link"
test -x "$profile/bin/guile" && ! test -x "$profile/bin/make"
+ # Switch to the rolled generation and switch back.
+ guix package -p "$profile" --switch-generation=2
+ test "`readlink_base "$profile"`" = "$profile-2-link"
+ guix package -p "$profile" --switch-generation=-1
+ test "`readlink_base "$profile"`" = "$profile-1-link"
+
+ # Switching to a non-existing generation does not change the current one.
+ guix package -p "$profile" --switch-generation=99
+ test "`readlink_base "$profile"`" = "$profile-1-link"
+
# Move to the empty profile.
for i in `seq 1 3`
do
@@ -132,10 +142,12 @@ then
grep "`guix build -e "$boot_make"`" "$profile/manifest"
# Make a "hole" in the list of generations, and make sure we can
- # roll back "over" it.
+ # roll back and switch "over" it.
rm "$profile-1-link"
guix package --bootstrap -p "$profile" --roll-back
test "`readlink_base "$profile"`" = "$profile-0-link"
+ guix package -p "$profile" --switch-generation=+1
+ test "`readlink_base "$profile"`" = "$profile-2-link"
# Make sure LIBRARY_PATH gets listed by `--search-paths'.
guix package --bootstrap -p "$profile" -i guile-bootstrap -i gcc-bootstrap
--
2.1.2
