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* Help to workaround libgit2 fetch refs issue
@ 2022-03-02 18:31 Phil
  2022-03-02 21:06 ` Liliana Marie Prikler
  0 siblings, 1 reply; 7+ messages in thread
From: Phil @ 2022-03-02 18:31 UTC (permalink / raw)
  To: Guix Devel

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Hi Guixers,

I raised an issue on libgit2 which effects the use of Guix with SSH git
clones and additional references:
https://github.com/libgit2/libgit2/issues/6183

The issue in summary is that if I want to build off a non-standard git
reference (say, a Pull Request), then even if I update my git config to
include that, eg:
remote.origin.fetch=+refs/pull-requests/*/merge:refs/remotes/origin/pr/*

libgit2's* initial clone* will not pull down the extra refs, despite this
being the behaviour of the git command line tool proper.  After the initial
clone, the git config is adhered to.

In Guix this means that the first time I build a PR it fails, and I have to
do something like "guix build  foo | guix build foo" which is at best a
clumsy hack, but it works!

Whilst the proper solution will be be done in libgit2 I was thinking if I
could quickly improve on my double-build workaround *without* having to
change Guix itself here (by *always *fetching):
https://github.com/guix-mirror/guix/blob/6adce1538d2df6fa2d68abc13ae94e2fa826d124/guix/git.scm#L466

If nothing else I was hoping to learn a bit more about how packages were
compiled as the details are a bit of blindspot for me!  So my plan was to
duplicate the git-checkout record and it's G-Exp compiler such that I could
redirect to a modified version of  update-cached-checkout when the source
is read from the package.

(I should also mention that the far simpler option of providing a new
"fetch" function like url-fetch or git-fetch doesn't work for me as the
repo I'm accessing happens to require SSH authentication and thus I'm using
the method as outlined here:  http://issues.guix.gnu.org/issue/31285#4 )

So I have something like:
    (package
      (name "my-test-repo")
      (version production-version)
      (source
       (git-checkout*-x-refs*
        (url "ssh://git@bitbucket:7999/ea/my-test-repo.git")
        (commit commit-production)))
      (build-system python-build-system)
      and so on....

The code I've naively duplicated is at the bottom of this e-mail - it
builds OK, so is syntactically correct, but fails when I reference it in a
package like above.  Having the record and git code as part of my local
channel is wrong, I know, but I'm looking a short term workaround with the
least disruptive footprint whilst I implement and then wait for release of
the strategic solution, probably in libgit2.

I suspect the reason for the failure is that I'd have to import my new
duplicated module somewhere in the Guix core code to make this work - i.e.
having the code in the channel is never going to work?

I was wondering if anyway could confirm this and/or give me a pointer of
where the compliation occurs (where the record in the source is handled and
compiled into a git clone) - even if my approach is (quite possibly)
unviable, I'd like to understand why!


Thanks,
Phil.


$ guix build -L /home/phil/git/guix/guix-packages/packages my-test-repo

guix build: warning: source expression failed to match any pattern
error: git-checkout-x-refs: unbound variable
hint: Did you forget `(use-modules (my-tools git))'?

guix build: error: my-test-repo: unknown package

_________________________________________________

I put this in /home/phil/git/guix/guix-packages/package/my-tools/git.scm-
I've marked the actual change in *bold *- everything else is just
boilerplate.

;; -*- mode: scheme; eval: (guix-devel-mode 1);
geiser-scheme-implementation: guile -*-

(define-module (my-tools git)
  #:use-module (git) ;; libgit
  #:use-module (guix git) ;; CAREFUL could clash!
  #:use-module (guix records) ;; define-record-type*
  #:use-module (guix gexp)
  #:use-module (ice-9 ftw) ;; scandir
  #:use-module (ice-9 match)
  #:use-module (srfi srfi-11) ;; let*-values
  #:export (git-checkout-x-refs
            git-checkout-x-refs?
            git-checkout-x-refs-url
            git-checkout-x-refs-branch
            git-checkout-x-refs-commit
            git-checkout-z-refs-recursive?))

;; local functions stolen from guix git
(define clone/swh-fallback (@@ (guix git) clone/swh-fallback))
(define with-libgit2 (@@ (guix git) with-libgit2))

;;;
;;; Checkouts.
;;;

;; Representation of the "latest" checkout of a branch or a specific commit.
;; Shadows git-checkout but uses difference function to get the repo.
(define-record-type* <git-checkout-x-refs>
  git-checkout-x-refs make-git-checkout-x-refs
  git-checkout-x-refs?
  (url     git-checkout-x-refs-url)
  (branch  git-checkout-x-refs-branch (default #f))
  (commit  git-checkout-x-refs-commit (default #f))      ;#f | tag | commit
  (recursive? git-checkout-x-refs-recursive? (default #f)))


(define* (update-cached-checkout-x-ref url
                                 #:key
                                 (ref '())
                                 recursive?
                                 (check-out? #t)
                                 starting-commit
                                 (log-port (%make-void-port "w"))
                                 (cache-directory
                                  (url-cache-directory
                                   url (%repository-cache-directory)
                                   #: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
provided) as returned by 'commit-relation'.
REF is pair whose key is [branch | commit | tag | tag-or-commit ] and value
the associated data: [<branch name> | <sha1> | <tag name> | <string>].
If REF is the empty list, the remote HEAD is used.
When RECURSIVE? is true, check out submodules as well, if any.
When CHECK-OUT? is true, reset the cached working tree to REF; otherwise
leave
it unchanged."
  (define (cache-entries directory)
    (filter-map (match-lambda
                  ((or "." "..")
                   #f)
                  (file
                   (string-append directory "/" file)))
                (or (scandir directory) '())))

  (define canonical-ref
    ;; We used to require callers to specify "origin/" for each branch,
which
    ;; made little sense since the cache should be transparent to them.  So
    ;; here we append "origin/" if it's missing and otherwise keep it.
    (match ref
      (() '(symref . "refs/remotes/origin/HEAD"))
      (('branch . branch)
       `(branch . ,(if (string-prefix? "origin/" branch)
                       branch
                       (string-append "origin/" branch))))
      (_ ref)))

  (with-libgit2
   (let* ((cache-exists? (openable-repository? cache-directory))
          (repository    (if cache-exists?
                             (repository-open cache-directory)
                             (clone/swh-fallback url ref
cache-directory)))) ;; if the cache doesn't exist, clone


*     ;; Always fetch remote, even if it has not been cloned just before.
   (when ;;(and cache-exists?                (not (reference-available?
repository ref)) ;;)*
       (remote-fetch (remote-lookup repository "origin")
                     #:fetch-options (make-default-fetch-options)))
     (when recursive?
       (update-submodules repository #:log-port log-port
                          #:fetch-options (make-default-fetch-options)))

     ;; Note: call 'commit-relation' from here because it's more efficient
     ;; than letting users re-open the checkout later on.
     (let* ((oid      (if check-out?
                          (switch-to-ref repository canonical-ref)
                          (object-id
                           (resolve-reference repository canonical-ref))))
            (new      (and starting-commit
                           (commit-lookup repository oid)))
            (old      (and starting-commit
                           (false-if-git-not-found
                            (commit-lookup repository
                                           (string->oid starting-commit)))))
            (relation (and starting-commit
                           (if old
                               (commit-relation old new)
                               'unrelated))))

       ;; Reclaim file descriptors and memory mappings associated with
       ;; REPOSITORY as soon as possible.
       (repository-close! repository)

       ;; Update CACHE-DIRECTORY's mtime to so the cache logic sees it.
       (match (gettimeofday)
         ((seconds . microseconds)
          (let ((nanoseconds (* 1000 microseconds)))
            (utime cache-directory
                   seconds seconds
                   nanoseconds nanoseconds))))

       ;; When CACHE-DIRECTORY is a sub-directory of the default cache
       ;; directory, remove expired checkouts that are next to it.
       (let ((parent (dirname cache-directory)))
         (when (string=? parent (%repository-cache-directory))
           (maybe-remove-expired-cache-entries parent cache-entries
                                               #:entry-expiration
                                               cached-checkout-expiration
                                               #:delete-entry
delete-checkout
                                               #:cleanup-period

 %checkout-cache-cleanup-period)))

       (values cache-directory (oid->string oid) relation)))))



(define* (latest-repository-commit-x-ref store url
                                   #:key
                                   recursive?
                                   (log-port (%make-void-port "w"))
                                   (cache-directory
                                    (%repository-cache-directory))
                                   (ref '()))
  "Return two values: the content of the git repository at URL copied into a
store directory and the sha1 of the top level commit in this directory.  The
reference to be checkout, once the repository is fetched, is specified by
REF.
REF is pair whose key is [branch | commit | tag] and value the associated
data, respectively [<branch name> | <sha1> | <tag name>].  If REF is the
empty
list, the remote HEAD is used.
When RECURSIVE? is true, check out submodules as well, if any.
Git repositories are kept in the cache directory specified by
%repository-cache-directory parameter.
Log progress and checkout info to LOG-PORT."
  (define (dot-git? file stat)
    (and (string=? (basename file) ".git")
         (or (eq? 'directory (stat:type stat))

             ;; Submodule checkouts end up with a '.git' regular file that
             ;; contains metadata about where their actual '.git' directory
             ;; lives.
             (and recursive?
                  (eq? 'regular (stat:type stat))))))

  (format log-port "updating checkout of '~a'...~%" url)
  (let*-values
      (((checkout commit _)
        (update-cached-checkout-x-ref url
                                #:recursive? recursive?
                                #:ref ref
                                #:cache-directory
                                (url-cache-directory url cache-directory
                                                     #:recursive?
                                                     recursive?)
                                #:log-port log-port))
       ((name)
        (url+commit->name url commit)))
    (format log-port "retrieved commit ~a~%" commit)
    (values (add-to-store store name #t "sha256" checkout
                          #:select? (negate dot-git?))
            commit)))



(define* (latest-repository-commit-x-refs* url #:key ref recursive?
log-port)
  ;; Monadic variant of 'latest-repository-commit-x-refs'.
  (lambda (store)
    ;; The caller--e.g., (guix scripts build)--may not handle 'git-error' so
    ;; translate it into '&message' conditions that we know will be properly
    ;; handled.
    (catch 'git-error
      (lambda ()
        (values (latest-repository-commit-x-ref store url
                                               #:ref ref
                                               #:recursive? recursive?
                                               #:log-port log-port)
                store))
      (lambda (key error . _)
        (raise (condition
                (&message
                 (message
                  (match ref
                    (('commit . commit)
                     (format #f (G_ "cannot fetch commit ~a from ~a: ~a")
                             commit url (git-error-message error)))
                    (('branch . branch)
                     (format #f (G_ "cannot fetch branch '~a' from ~a: ~a")
                             branch url (git-error-message error)))
                    (_
                     (format #f (G_ "Git failure while fetching ~a: ~a")
                             url (git-error-message error))))))))))))



(define-gexp-compiler (git-checkout-x-refs-compiler (checkout
<git-checkout-x-refs>)
                                                    system target)
  ;; "Compile" CHECKOUT by updating the local checkout and adding it to the
  ;; store.  Handle the libgit2 issue by fetching refs, even on a clone.
  (match checkout
    (($ <git-checkout-x-refs> url branch commit recursive?)
     (latest-repository-commit-x-refs* url
                                       #:ref (cond (commit
                                                    `(tag-or-commit .
,commit))
                                                   (branch
                                                    `(branch . ,branch))
                                                   (else '()))
                                       #:recursive? recursive?
                                       #:log-port (current-error-port)))))

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^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-04-30  9:34 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-03-02 18:31 Help to workaround libgit2 fetch refs issue Phil
2022-03-02 21:06 ` Liliana Marie Prikler
2022-03-03 18:20   ` Phil
2022-03-04  9:34     ` Phil
2022-03-04 17:43       ` Liliana Marie Prikler
2022-03-05 11:57         ` Phil
2022-04-30  9:28           ` zimoun

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