[bug#65352] Fix time-machine and network

[Simon Tournier]

Hi Ludo,

On Wed, 13 Sep 2023 at 22:16, Ludovic Courtès <ludo@gnu.org> wrote:

>> +    (('commit . (? commit-id? commit))
>> +     (let ((oid (string->oid commit)))
>> +       (->bool (commit-lookup repository oid))))
>> +    ((or ('tag . str)
>> +         ('tag-or-commit . str))
>> +     (false-if-git-not-found
>> +      (->bool (resolve-reference repository ref))))
>
> IIUC, the differences compared to what we had are:
>
>   1. 'tag references are now handled on the fast path
>      (‘reference-available?’ can return #t);
>
>   2. short commit strings are now always on the slow path
>      (‘reference-available?’ always returns #f).
>
> Is that correct?

No, or I am missing some details.

> It would be nice to have #1 without #2.

It’s already the case because of that:

         (option '("commit") #t #f
                 (lambda (opt name arg result)
                   (alist-cons 'ref `(tag-or-commit . ,arg) result)))

Currently, the heuristic to determine if it is a tag or a commit is
implemented by ’resolve-reference’.

Somehow, considering the command-line parser, the alternative is:

    #1 and #2 on the fast path (the patch)
 or
    #1 and #2 on the slow path (the current implementation)

Let ’pk’ (see below) to convince you. :-)

Before the proposed patch:

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix time-machine --commit=v1.4.0 -- describe

;;; (ref (tag-or-commit . "v1.4.0"))

;;; (reference-available? #f)

;;; (remote-fetch NETWORK)
  C-c C-c

$ ./pre-inst-env guix time-machine --commit=8e2f32c -- describe

;;; (ref (tag-or-commit . "8e2f32c"))

;;; (reference-available? #f)

;;; (remote-fetch NETWORK)
  C-c C-c
--8<---------------cut here---------------end--------------->8---

After the proposed patch:

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix time-machine --commit=v1.4.0 -- describe

;;; (ref (tag-or-commit . "v1.4.0"))

;;; (reference-available? #t)
  guix 8e2f32c
    repository URL: https://git.savannah.gnu.org/git/guix.git
    commit: 8e2f32cee982d42a79e53fc1e9aa7b8ff0514714

$ ./pre-inst-env guix time-machine --commit=8e2f32c -- describe

;;; (ref (tag-or-commit . "8e2f32c"))

;;; (reference-available? #t)
  guix 8e2f32c
    repository URL: https://git.savannah.gnu.org/git/guix.git
    commit: 8e2f32cee982d42a79e53fc1e9aa7b8ff0514714
--8<---------------cut here---------------end--------------->8---


Cheers,
simon

--8<---------------cut here---------------start------------->8---
diff --git a/guix/git.scm b/guix/git.scm
index 1cb87a45607b..c927555cce18 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -481,6 +481,8 @@ (define* (update-cached-checkout url
                              (repository-open cache-directory)
                              (clone/swh-fallback url ref cache-directory))))
      ;; Only fetch remote if it has not been cloned just before.
+     (pk 'ref ref)
+     (pk 'reference-available? (reference-available? repository ref))
      (when (and cache-exists?
                 (not (reference-available? repository ref)))
        (remote-fetch (remote-lookup repository "origin")
--8<---------------cut here---------------end--------------->8---