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

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

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