[bug#64737] [PATCH 1/2] git: Clarify commit relation reference in doc.

[bug#64737] [PATCH 1/2] git: Clarify commit relation reference in doc.

[Maxim Cournoyer]

* guix/git.scm (update-cached-checkout): Clarify that it is the relation of
STARTING-COMMIT that is returned, relative to the new commit, not the other
way around.
---

 guix/git.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/guix/git.scm b/guix/git.scm
index be20cde019..dbc3b7caa7 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -439,7 +439,7 @@ (define* (update-cached-checkout url
                                    #:recursive? recursive?)))
   "Update the cached checkout of URL to REF in CACHE-DIRECTORY.  Return three
 values: the cache directory name, and the SHA1 commit (a string) corresponding
-to REF, and the relation of the new commit relative to STARTING-COMMIT (if
+to REF, and the relation of STARTING-COMMIT relative to the new commit (if
 provided) as returned by 'commit-relation'.
 
 REF is pair whose key is [branch | commit | tag | tag-or-commit ] and value

base-commit: 1d837aaa32a3a2de8f4a1ac391f92effba50834e
-- 
2.41.0

[bug#64737] [PATCH 2/2] scripts: time-machine: Error when attempting to visit too old commits.

[Maxim Cournoyer]

* doc/guix.texi (Invoking guix time-machine): Document limitation.
* guix/scripts/time-machine.scm (%oldest-possible-commit): New variable.
(guix-time-machine): Raise an error when the channel commit is too old.

Suggested-by: Simon Tournier <zimon.toutoune@gmail.com>
---

 doc/guix.texi                 |  6 ++++++
 guix/scripts/time-machine.scm | 23 ++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 1d8ebcd72f..30fef813c0 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5056,6 +5056,12 @@ Invoking guix time-machine
 large number of packages; the result is cached though and subsequent
 commands targeting the same commit are almost instantaneous.
 
+Due to @command{guix time-machine} relying on the ``inferiors''
+mechanism (@pxref{Inferiors}), the oldest commit it can travel to is
+commit @samp{2ca299caf} (``Add (guix inferior) and (guix scripts
+repl).''), dated July 10@sup{th}, 2018.  An error is returned when
+attempting to navigate to older commits.
+
 @quotation Note
 The history of Guix is immutable and @command{guix time-machine}
 provides the exact same software as they are in a specific Guix
diff --git a/guix/scripts/time-machine.scm b/guix/scripts/time-machine.scm
index d7c71ef705..36a40a1538 100644
--- a/guix/scripts/time-machine.scm
+++ b/guix/scripts/time-machine.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2019 Konrad Hinsen <konrad.hinsen@fastmail.net>
 ;;; Copyright © 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2021 Simon Tournier <zimon.toutoune@gmail.com>
+;;; Copyright © 2023 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -19,13 +20,15 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix scripts time-machine)
+  #:use-module (guix channels)
+  #:use-module (guix diagnostics)
   #:use-module (guix ui)
   #:use-module (guix scripts)
   #:use-module (guix inferior)
   #:use-module (guix store)
   #:use-module (guix status)
   #:use-module ((guix git)
-                #:select (with-git-error-handling))
+                #:select (update-cached-checkout with-git-error-handling))
   #:use-module ((guix utils)
                 #:select (%current-system))
   #:use-module ((guix scripts pull)
@@ -38,9 +41,16 @@ (define-module (guix scripts time-machine)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-37)
+  #:use-module (srfi srfi-71)
   #:export (guix-time-machine))
 
+;;; The commit introducing the 'inferiors' mechanism; it is the oldest commit
+;;; that can be travelled to.
+(define %oldest-possible-commit
+  "2ca299caf64489f4e1e665ec1158fb0309b0b565")
+
 \f
 ;;;
 ;;; Command-line options.
@@ -139,9 +149,20 @@ (define-command (guix-time-machine . args)
     (with-git-error-handling
      (let* ((opts         (parse-args args))
             (channels     (channel-list opts))
+            (guix-channel (find guix-channel? channels))
             (command-line (assoc-ref opts 'exec))
+            (ref          (assoc-ref opts 'ref))
+            (checkout commit relation (update-cached-checkout
+                                       (channel-url guix-channel)
+                                       #:ref (or ref '())
+                                       #:starting-commit
+                                       %oldest-possible-commit))
             (substitutes?  (assoc-ref opts 'substitutes?))
             (authenticate? (assoc-ref opts 'authenticate-channels?)))
+       (unless (memq relation '(ancestor self))
+         (raise (formatted-message
+                 (G_ "cannot travel past commit `~a' from July 10th, 2018")
+                 (string-take %oldest-possible-commit 12))))
        (when command-line
          (let* ((directory
                  (with-store store
-- 
2.41.0

[bug#64737] [PATCH 2/2] scripts: time-machine: Error when attempting to visit too old commits.

[Maxim Cournoyer]

Hi,

Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:

> * doc/guix.texi (Invoking guix time-machine): Document limitation.
> * guix/scripts/time-machine.scm (%oldest-possible-commit): New variable.
> (guix-time-machine): Raise an error when the channel commit is too old.

So I did the following test:

$ guix time-machine --commit=2ca299caf -- shell hello -- hello

which after building Guile 2.2.4 crashed with:

--8<---------------cut here---------------start------------->8---
construction de /gnu/store/rj2g4x23lqyaq16471qm94xp90slxp3h-compute-guix-derivation.drv...
|déchargement de la construction de /gnu/store/rj2g4x23lqyaq16471qm94xp90slxp3h-compute-guix-derivation.drv sur « 10.0.0.7 »
Computing Guix derivation for 'x86_64-linux'...  Backtrace:
-           5 (primitive-load "/gnu/store/b70mihsj9xx0xxp6izliqb5vm4…")
In ice-9/eval.scm:
    155:9  4 (_ _)
    159:9  3 (_ #(#(#(#(#(#(#(#(#(#(#(…) …) …) …) …) …) …) …) …) …) …))
   173:47  2 (_ #(#(#(#(#(#(#(#(#(#(#(…) …) …) …) …) …) …) …) …) …) …))
In ./guix/self.scm:
    932:4  1 (guix-derivation "/gnu/store/yfn2s94i5bvwr7j7r6xcnivwg…" …)
    903:2  0 (guile-for-build "3.0")

./guix/self.scm:903:2: In procedure guile-for-build:
Throw to key `match-error' with args `("match" "no matching pattern" "3.0")'.
Backtrace:
In ice-9/boot-9.scm:
  1752:10 19 (with-exception-handler _ _ #:unwind? _ # _)
In guix/store.scm:
   659:37 18 (thunk)
In guix/status.scm:
    839:4 17 (call-with-status-report _ _)
In guix/store.scm:
   1298:8 16 (call-with-build-handler #<procedure 7fbf6ea46930 at g…> …)
  2168:25 15 (run-with-store #<store-connection 256.99 7fbf7448ea50> …)
In guix/inferior.scm:
    927:8 14 (_ _)
In guix/channels.scm:
    982:2 13 (_ _)
    924:2 12 (_ _)
In ./guix/monads.scm:
    487:9 11 (_ _)
In guix/store.scm:
   1996:8 10 (_ _)
In guix/channels.scm:
   675:14  9 (_ #<store-connection 256.99 7fbf7448ea50>)
In guix/store.scm:
  2168:25  8 (run-with-store #<store-connection 256.99 7fbf7448ea50> …)
   1298:8  7 (call-with-build-handler _ _)
   1298:8  6 (call-with-build-handler #<procedure 7fbf6f7bd8d0 at g…> …)
In guix/channels.scm:
   690:14  5 (_)
In guix/store.scm:
  2168:25  4 (run-with-store #<store-connection 256.99 7fbf7448ea50> …)
In ice-9/eval.scm:
   191:27  3 (_ #(#(#<directory (build-self) 7fbf6c40d960> #<pr…>) …))
In ice-9/boot-9.scm:
   2007:7  2 (error _ . _)
  1685:16  1 (raise-exception _ #:continuable? _)
  1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
invalid build result (#<derivation /gnu/store/rj2g4x23lqyaq16471qm94xp90slxp3h-compute-guix-derivation.drv => /gnu/store/b70mihsj9xx0xxp6izliqb5vm462yifl-compute-guix-derivation 7fbf5bf82c30> "")
--8<---------------cut here---------------end--------------->8---

Thoughts?

-- 
Thanks,
Maxim