[PATCH 0/2] Download Git checkouts from Software Heritage as a last resort

DoneSubmitted by Ludovic Courtès.
One participant
  • Ludovic Courtès
Ludovic Courtès wrote on 19 Nov 2018 17:13
(address . guix-patches@gnu.org)(name . Ludovic Courtès)(address . ludo@gnu.org)
Hello Guix!
This patch series adds the Software Heritage (SWH) client library initiallydiscussed at:
Furthermore, it uses it in (guix git-download) to download code from SWHwhen it is unavailable upstream and on our servers. This bit relies onthe “vault” API of SWH, which allows you to fetch a checkout as a tarball.Not all revisions are readily available as tarballs, understandably, sothe vault API has a mechanism that allows you to request the “cooking”of a specific checkout. Cooking is asynchronous and can take some time.
When downloading over SWH, the ‘swh-download’ procedure first resolvesthe tag (if it’s a tag), then tries to download the corresponding tarballfrom the vault. If the vault doesn’t have it yet, it sends a cookingrequest and waits for it to complete by periodically checking the cookingstatus.
In the future, we should provide a “lister” and “loader” so that SWH canregularly obtain a list of Guix packages with their source URL andcommit/tag:
The SWH team is also considering pre-cooking all VCS tags such thatevery time we refer to a tag, we can be sure its contents are alreadyavailable in the vault:
Feedback welcome!
Ludovic Courtès (2): Add (guix swh). git-download: Download from Software Heritage as a last resort.
Makefile.am | 1 + guix/git-download.scm | 64 +++-- guix/swh.scm | 551 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 596 insertions(+), 20 deletions(-) create mode 100644 guix/swh.scm
-- 2.19.1
Ludovic Courtès wrote on 19 Nov 2018 17:24
[PATCH 2/2] git-download: Download from Software Heritage as a last resort.
(address . 33432@debbugs.gnu.org)(name . Ludovic Courtès)(address . ludovic.courtes@inria.fr)
From: Ludovic Courtès <ludovic.courtes@inria.fr>
* guix/git-download.scm (git-fetch)[inputs]: Add gzip and tar when'git-reference-recursive?' is false.[guile-json, gnutls]: New variables.[modules]: Add (guix swh).[build]: Wrap in 'with-extensions'. Add call to 'swh-download'.--- guix/git-download.scm | 64 +++++++++++++++++++++++++++++-------------- 1 file changed, 44 insertions(+), 20 deletions(-)
Toggle diff (93 lines)diff --git a/guix/git-download.scm b/guix/git-download.scmindex fa94fad8f8..2689658af8 100644--- a/guix/git-download.scm+++ b/guix/git-download.scm@@ -74,11 +74,22 @@ HASH-ALGO (a symbol). Use NAME as the file name, or a generic name if #f." ;; available so that 'git submodule' works. (if (git-reference-recursive? ref) (standard-packages)- '()))++ ;; The 'swh-download' procedure requires tar and gzip.+ `(("gzip" ,(module-ref (resolve-interface '(gnu packages compression))+ 'gzip))+ ("tar" ,(module-ref (resolve-interface '(gnu packages base))+ 'tar))))) (define zlib (module-ref (resolve-interface '(gnu packages compression)) 'zlib)) + (define guile-json+ (module-ref (resolve-interface '(gnu packages guile)) 'guile-json))++ (define gnutls+ (module-ref (resolve-interface '(gnu packages tls)) 'gnutls))+ (define config.scm (scheme-file "config.scm" #~(begin@@ -93,30 +104,43 @@ HASH-ALGO (a symbol). Use NAME as the file name, or a generic name if #f." (delete '(guix config) (source-module-closure '((guix build git) (guix build utils)- (guix build download-nar))))))+ (guix build download-nar)+ (guix swh)))))) (define build (with-imported-modules modules- #~(begin- (use-modules (guix build git)- (guix build utils)- (guix build download-nar)- (ice-9 match))+ (with-extensions (list guile-json gnutls) ;for (guix swh)+ #~(begin+ (use-modules (guix build git)+ (guix build utils)+ (guix build download-nar)+ (guix swh)+ (ice-9 match)) - ;; The 'git submodule' commands expects Coreutils, sed,- ;; grep, etc. to be in $PATH.- (set-path-environment-variable "PATH" '("bin")- (match '#+inputs- (((names dirs outputs ...) ...)- dirs)))+ (define recursive?+ (call-with-input-string (getenv "git recursive?") read)) - (or (git-fetch (getenv "git url") (getenv "git commit")- #$output- #:recursive? (call-with-input-string- (getenv "git recursive?")- read)- #:git-command (string-append #+git "/bin/git"))- (download-nar #$output)))))+ ;; The 'git submodule' commands expects Coreutils, sed,+ ;; grep, etc. to be in $PATH.+ (set-path-environment-variable "PATH" '("bin")+ (match '#+inputs+ (((names dirs outputs ...) ...)+ dirs)))++ (setvbuf (current-output-port) 'line)+ (setvbuf (current-error-port) 'line)++ (or (git-fetch (getenv "git url") (getenv "git commit")+ #$output+ #:recursive? recursive?+ #:git-command (string-append #+git "/bin/git"))+ (download-nar #$output)++ ;; As a last resort, attempt to download from Software Heritage.+ ;; XXX: Currently recursive checkouts are not supported.+ (and (not recursive?)+ (swh-download (getenv "git url") (getenv "git commit")+ #$output))))))) (mlet %store-monad ((guile (package->derivation guile system))) (gexp->derivation (or name "git-checkout") build-- 2.19.1
Ludovic Courtès wrote on 19 Nov 2018 17:24
[PATCH 1/2] Add (guix swh).
(address . 33432@debbugs.gnu.org)(name . Ludovic Courtès)(address . ludovic.courtes@inria.fr)
From: Ludovic Courtès <ludovic.courtes@inria.fr>
* guix/swh.scm: New file.* Makefile.am (MODULES): Add it.--- Makefile.am | 1 + guix/swh.scm | 551 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 552 insertions(+) create mode 100644 guix/swh.scm
Toggle diff (571 lines)diff --git a/Makefile.am b/Makefile.amindex c63b65ba56..63266bd96b 100644--- a/Makefile.am+++ b/Makefile.am@@ -74,6 +74,7 @@ MODULES = \ guix/discovery.scm \ guix/git-download.scm \ guix/hg-download.scm \+ guix/swh.scm \ guix/monads.scm \ guix/monad-repl.scm \ guix/gexp.scm \diff --git a/guix/swh.scm b/guix/swh.scmnew file mode 100644index 0000000000..c188e17c69--- /dev/null+++ b/guix/swh.scm@@ -0,0 +1,551 @@+;;; GNU Guix --- Functional package management for GNU+;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>+;;;+;;; This file is part of GNU Guix.+;;;+;;; GNU Guix is free software; you can redistribute it and/or modify it+;;; under the terms of the GNU General Public License as published by+;;; the Free Software Foundation; either version 3 of the License, or (at+;;; your option) any later version.+;;;+;;; GNU Guix is distributed in the hope that it will be useful, but+;;; WITHOUT ANY WARRANTY; without even the implied warranty of+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the+;;; GNU General Public License for more details.+;;;+;;; You should have received a copy of the GNU General Public License+;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.++(define-module (guix swh)+ #:use-module (guix base16)+ #:use-module (guix build utils)+ #:use-module ((guix build syscalls) #:select (mkdtemp!))+ #:use-module (web client)+ #:use-module (web response)+ #:use-module (json)+ #:use-module (srfi srfi-1)+ #:use-module (srfi srfi-9)+ #:use-module (srfi srfi-11)+ #:use-module (srfi srfi-19)+ #:use-module (ice-9 match)+ #:use-module (ice-9 regex)+ #:use-module (ice-9 popen)+ #:use-module ((ice-9 ftw) #:select (scandir))+ #:export (origin?+ origin-id+ origin-type+ origin-url+ origin-visits+ lookup-origin++ visit?+ visit-date+ visit-origin+ visit-url+ visit-snapshot-url+ visit-status+ visit-number+ visit-snapshot++ branch?+ branch-name+ branch-target++ release?+ release-id+ release-name+ release-message+ release-target++ revision?+ revision-id+ revision-date+ revision-directory+ lookup-revision+ lookup-origin-revision++ content?+ content-checksums+ content-data-url+ content-length+ lookup-content++ directory-entry?+ directory-entry-name+ directory-entry-type+ directory-entry-checksums+ directory-entry-length+ directory-entry-permissions+ lookup-directory+ directory-entry-target++ vault-reply?+ vault-reply-id+ vault-reply-fetch-url+ vault-reply-object-id+ vault-reply-object-type+ vault-reply-progress-message+ vault-reply-status+ query-vault+ request-cooking+ vault-fetch++ swh-download))++;;; Commentary:+;;;+;;; This module provides bindings to the HTTP interface of Software Heritage.+;;; It allows you to browse the archive, look up revisions (such as SHA1+;;; commit IDs), "origins" (code hosting URLs), content (files), etc. See+;;; <https://archive.softwareheritage.org/api/> for more information.+;;;+;;; The high-level 'swh-download' procedure allows you to download a Git+;;; revision from Software Heritage, provided it is available.+;;;+;;; Code:++(define %swh-base-url+ ;; Presumably we won't need to change it.+ "https://archive.softwareheritage.org")++(define (swh-url path . rest)+ (define url+ (string-append %swh-base-url path+ (string-join rest "/" 'prefix)))++ ;; Ensure there's a trailing slash or we get a redirect.+ (if (string-suffix? "/" url)+ url+ (string-append url "/")))++(define-syntax-rule (define-json-reader json->record ctor spec ...)+ "Define JSON->RECORD as a procedure that converts a JSON representation,+read from a port, string, or hash table, into a record created by CTOR and+following SPEC, a series of field specifications."+ (define (json->record input)+ (let ((table (cond ((port? input)+ (json->scm input))+ ((string? input)+ (json-string->scm input))+ ((hash-table? input)+ input))))+ (let-syntax ((extract-field (syntax-rules ()+ ((_ table (field key json->value))+ (json->value (hash-ref table key)))+ ((_ table (field key))+ (hash-ref table key))+ ((_ table (field))+ (hash-ref table+ (symbol->string 'field))))))+ (ctor (extract-field table spec) ...)))))++(define-syntax-rule (define-json-mapping rtd ctor pred json->record+ (field getter spec ...) ...)+ "Define RTD as a record type with the given FIELDs and GETTERs, à la SRFI-9,+and define JSON->RECORD as a conversion from JSON to a record of this type."+ (begin+ (define-record-type rtd+ (ctor field ...)+ pred+ (field getter) ...)++ (define-json-reader json->record ctor+ (field spec ...) ...)))++(define %date-regexp+ ;; Match strings like "2014-11-17T22:09:38+01:00" or+ ;; "2018-09-30T23:20:07.815449+00:00"".+ (make-regexp "^([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2}):([0-9]{2})((\\.[0-9]+)?)([+-][0-9]{2}):([0-9]{2})$"))++(define (string->date* str)+ "Return a SRFI-19 date parsed from STR, a date string as returned by+Software Heritage."+ ;; We can't use 'string->date' because of the timezone format: SWH returns+ ;; "+01:00" when the '~z' template expects "+0100". So we roll our own!+ (or (and=> (regexp-exec %date-regexp str)+ (lambda (match)+ (define (ref n)+ (string->number (match:substring match n)))++ (make-date (let ((ns (match:substring match 8)))+ (if ns+ (string->number (string-drop ns 1))+ 0))+ (ref 6) (ref 5) (ref 4)+ (ref 3) (ref 2) (ref 1)+ (+ (* 3600 (ref 9)) ;time zone+ (if (< (ref 9) 0)+ (- (ref 10))+ (ref 10))))))+ str)) ;oops!++(define* (call url decode #:optional (method http-get)+ #:key (false-if-404? #t))+ "Invoke the endpoint at URL using METHOD. Decode the resulting JSON body+using DECODE, a one-argument procedure that takes an input port. When+FALSE-IF-404? is true, return #f upon 404 responses."+ (let*-values (((response port)+ (method url #:streaming? #t)))+ ;; See <https://archive.softwareheritage.org/api/#rate-limiting>.+ (match (assq-ref (response-headers response) 'x-ratelimit-remaining)+ (#f #t)+ ((? (compose zero? string->number))+ (throw 'swh-error url response))+ (_ #t))++ (cond ((= 200 (response-code response))+ (let ((result (decode port)))+ (close-port port)+ result))+ ((and false-if-404?+ (= 404 (response-code response)))+ (close-port port)+ #f)+ (else+ (close-port port)+ (throw 'swh-error url response)))))++(define-syntax define-query+ (syntax-rules (path)+ "Define a procedure that performs a Software Heritage query."+ ((_ (name args ...) docstring (path components ...)+ json->value)+ (define (name args ...)+ docstring+ (call (swh-url components ...) json->value)))))++;; <https://archive.softwareheritage.org/api/1/origin/git/url/https://github.com/guix-mirror/guix/>+(define-json-mapping <origin> make-origin origin?+ json->origin+ (id origin-id)+ (visits-url origin-visits-url "origin_visits_url")+ (type origin-type)+ (url origin-url))++;; <https://archive.softwareheritage.org/api/1/origin/52181937/visits/>+(define-json-mapping <visit> make-visit visit?+ json->visit+ (date visit-date "date" string->date*)+ (origin visit-origin)+ (url visit-url "origin_visit_url")+ (snapshot-url visit-snapshot-url "snapshot_url")+ (status visit-status)+ (number visit-number "visit"))++;; <https://archive.softwareheritage.org/api/1/snapshot/4334c3ed4bb208604ed780d8687fe523837f1bd1/>+(define-json-mapping <snapshot> make-snapshot snapshot?+ json->snapshot+ (branches snapshot-branches "branches" json->branches))++;; This is used for the "branches" field of snapshots.+(define-record-type <branch>+ (make-branch name target-type target-url)+ branch?+ (name branch-name)+ (target-type branch-target-type) ;release | revision+ (target-url branch-target-url))++(define (json->branches branches)+ (hash-map->list (lambda (key value)+ (make-branch key+ (string->symbol+ (hash-ref value "target_type"))+ (hash-ref value "target_url")))+ branches))++;; <https://archive.softwareheritage.org/api/1/release/1f44934fb6e2cefccbecd4fa347025349fa9ff76/>+(define-json-mapping <release> make-release release?+ json->release+ (id release-id)+ (name release-name)+ (message release-message)+ (target-type release-target-type "target_type" string->symbol)+ (target-url release-target-url "target_url"))++;; <https://archive.softwareheritage.org/api/1/revision/359fdda40f754bbf1b5dc261e7427b75463b59be/>+(define-json-mapping <revision> make-revision revision?+ json->revision+ (id revision-id)+ (date revision-date "date" string->date*)+ (directory revision-directory)+ (directory-url revision-directory-url "directory_url"))++;; <https://archive.softwareheritage.org/api/1/content/>+(define-json-mapping <content> make-content content?+ json->content+ (checksums content-checksums "checksums" json->checksums)+ (data-url content-data-url "data_url")+ (file-type-url content-file-type-url "filetype_url")+ (language-url content-language-url "language_url")+ (length content-length)+ (license-url content-license-url "license_url"))++(define (json->checksums checksums)+ (hash-map->list (lambda (key value)+ (cons key (base16-string->bytevector value)))+ checksums))++;; <https://archive.softwareheritage.org/api/1/directory/27c69c5d298a43096a53affbf881e7b13f17bdcd/>+(define-json-mapping <directory-entry> make-directory-entry directory-entry?+ json->directory-entry+ (name directory-entry-name)+ (type directory-entry-type "type"+ (match-lambda+ ("dir" 'directory)+ (str (string->symbol str))))+ (checksums directory-entry-checksums "checksums"+ (match-lambda+ (#f #f)+ (lst (json->checksums lst))))+ (id directory-entry-id "dir_id")+ (length directory-entry-length)+ (permissions directory-entry-permissions "perms")+ (target-url directory-entry-target-url "target_url"))++;; <https://archive.softwareheritage.org/api/1/origin/save/>+(define-json-mapping <save-reply> make-save-reply save-reply?+ json->save-reply+ (origin-url save-reply-origin-url "origin_url")+ (origin-type save-reply-origin-type "origin_type")+ (request-date save-reply-request-date "save_request_date"+ string->date*)+ (request-status save-reply-request-status "save_request_status"+ string->symbol)+ (task-status save-reply-task-status "save_task_status"+ (match-lambda+ ("not created" 'not-created)+ ((? string? str) (string->symbol str)))))++;; <https://docs.softwareheritage.org/devel/swh-vault/api.html#vault-api-ref>+(define-json-mapping <vault-reply> make-vault-reply vault-reply?+ json->vault-reply+ (id vault-reply-id)+ (fetch-url vault-reply-fetch-url "fetch_url")+ (object-id vault-reply-object-id "obj_id")+ (object-type vault-reply-object-type "obj_type" string->symbol)+ (progress-message vault-reply-progress-message "progress_message")+ (status vault-reply-status "status" string->symbol))++ +;;;+;;; RPCs.+;;;++(define-query (lookup-origin url)+ "Return an origin for URL."+ (path "/api/1/origin/git/url" url)+ json->origin)++(define-query (lookup-content hash type)+ "Return a content for HASH, of the given TYPE--e.g., \"sha256\"."+ (path "/api/1/content"+ (string-append type ":"+ (bytevector->base16-string hash)))+ json->content)++(define-query (lookup-revision id)+ "Return the revision with the given ID, typically a Git commit SHA1."+ (path "/api/1/revision" id)+ json->revision)++(define-query (lookup-directory id)+ "Return the directory with the given ID."+ (path "/api/1/directory" id)+ json->directory-entries)++(define (json->directory-entries port)+ (map json->directory-entry (json->scm port)))++(define (origin-visits origin)+ "Return the list of visits of ORIGIN, a record as returned by+'lookup-origin'."+ (call (swh-url (origin-visits-url origin))+ (lambda (port)+ (map json->visit (json->scm port)))))++(define (visit-snapshot visit)+ "Return the snapshot corresponding to VISIT."+ (call (swh-url (visit-snapshot-url visit))+ json->snapshot))++(define (branch-target branch)+ "Return the target of BRANCH, either a <revision> or a <release>."+ (match (branch-target-type branch)+ ('release+ (call (swh-url (branch-target-url branch))+ json->release))+ ('revision+ (call (swh-url (branch-target-url branch))+ json->revision))))++(define (lookup-origin-revision url tag)+ "Return a <revision> corresponding to the given TAG for the repository+coming from URL. Example:++ (lookup-origin-release \"https://github.com/guix-mirror/guix/\" \"v0.8\")+ => #<<revision> id: \"44941…\" …>++The information is based on the latest visit of URL available. Return #f if+URL could not be found."+ (match (lookup-origin url)+ (#f #f)+ (origin+ (match (origin-visits origin)+ ((visit . _)+ (let ((snapshot (visit-snapshot visit)))+ (match (and=> (find (lambda (branch)+ (string=? (string-append "refs/tags/" tag)+ (branch-name branch)))+ (snapshot-branches snapshot))+ branch-target)+ ((? release? release)+ (release-target release))+ ((? revision? revision)+ revision)+ (#f ;tag not found+ #f))))+ (()+ #f)))))++(define (release-target release)+ "Return the revision that is the target of RELEASE."+ (match (release-target-type release)+ ('revision+ (call (swh-url (release-target-url release))+ json->revision))))++(define (directory-entry-target entry)+ "If ENTRY, a directory entry, has type 'directory, return its list of+directory entries; if it has type 'file, return its <content> object."+ (call (swh-url (directory-entry-target-url entry))+ (match (directory-entry-type entry)+ ('file json->content)+ ('directory json->directory-entries))))++(define* (save-origin url #:optional (type "git"))+ "Request URL to be saved."+ (call (swh-url "/api/1/origin/save" type "url" url) json->save-reply+ http-post))++(define-query (save-origin-status url type)+ "Return the status of a /save request for URL and TYPE (e.g., \"git\")."+ (path "/api/1/origin/save" type "url" url)+ json->save-reply)++(define-query (query-vault id kind)+ "Ask the availability of object ID and KIND to the vault, where KIND is+'directory or 'revision. Return #f if it could not be found, or a+<vault-reply> on success."+ ;; <https://docs.softwareheritage.org/devel/swh-vault/api.html#vault-api-ref>+ ;; There's a single format supported for directories and revisions and for+ ;; now, the "/format" bit of the URL *must* be omitted.+ (path "/api/1/vault" (symbol->string kind) id)+ json->vault-reply)++(define (request-cooking id kind)+ "Request the cooking of object ID and KIND (one of 'directory or 'revision)+to the vault. Return a <vault-reply>."+ (call (swh-url "/api/1/vault" (symbol->string kind) id)+ json->vault-reply+ http-post))++(define* (vault-fetch id kind+ #:key (log-port (current-error-port)))+ "Return an input port from which a bundle of the object with the given ID+and KIND (one of 'directory or 'revision) can be retrieved, or #f if the+object could not be found.++For a directory, the returned stream is a gzip-compressed tarball. For a+revision, it is a gzip-compressed stream for 'git fast-import'."+ (let loop ((reply (query-vault id kind)))+ (match reply+ (#f+ (and=> (request-cooking id kind) loop))+ (_+ (match (vault-reply-status reply)+ ('done+ ;; Fetch the bundle.+ (let-values (((response port)+ (http-get (swh-url (vault-reply-fetch-url reply))+ #:streaming? #t)))+ (if (= (response-code response) 200)+ port+ (begin ;shouldn't happen+ (close-port port)+ #f))))+ ('failed+ ;; Upon failure, we're supposed to try again.+ (format log-port "SWH vault: failure: ~a~%"+ (vault-reply-progress-message reply))+ (format log-port "SWH vault: retrying...~%")+ (loop (request-cooking id kind)))+ ((and (or 'new 'pending) status)+ ;; Wait until the bundle shows up.+ (let ((message (vault-reply-progress-message reply)))+ (when (eq? 'new status)+ (format log-port "SWH vault: \+requested bundle cooking, waiting for completion...~%"))+ (when (string? message)+ (format log-port "SWH vault: ~a~%" message))++ ;; Wait long enough so we don't exhaust our maximum number of+ ;; requests per hour too fast (as of this writing, the limit is 60+ ;; requests per hour per IP address.)+ (sleep (if (eq? status 'new) 60 30))++ (loop (query-vault id kind)))))))))++ +;;;+;;; High-level interface.+;;;++(define (commit-id? reference)+ "Return true if REFERENCE is likely a commit ID, false otherwise---e.g., if+it is a tag name."+ (and (= (string-length reference) 40)+ (string-every char-set:hex-digit reference)))++(define (call-with-temporary-directory proc) ;FIXME: factorize+ "Call PROC with a name of a temporary directory; close the directory and+delete it when leaving the dynamic extent of this call."+ (let* ((directory (or (getenv "TMPDIR") "/tmp"))+ (template (string-append directory "/guix-directory.XXXXXX"))+ (tmp-dir (mkdtemp! template)))+ (dynamic-wind+ (const #t)+ (lambda ()+ (proc tmp-dir))+ (lambda ()+ (false-if-exception (delete-file-recursively tmp-dir))))))++(define (swh-download url reference output)+ "Download from Software Heritage a checkout of the Git tag or commit+REFERENCE originating from URL, and unpack it in OUTPUT. Return #t on success+and #f on failure.++This procedure uses the \"vault\", which contains \"cooked\" directories in+the form of tarballs. If the requested directory is not cooked yet, it will+wait until it becomes available, which could take several minutes."+ (match (if (commit-id? reference)+ (lookup-revision reference)+ (lookup-origin-revision url reference))+ ((? revision? revision)+ (call-with-temporary-directory+ (lambda (directory)+ (let ((input (vault-fetch (revision-directory revision) 'directory))+ (tar (open-pipe* OPEN_WRITE "tar" "-C" directory "-xzvf" "-")))+ (dump-port input tar)+ (close-port input)+ (let ((status (close-pipe tar)))+ (unless (zero? status)+ (error "tar extraction failure" status)))++ (match (scandir directory)+ (("." ".." sub-directory)+ (copy-recursively (string-append directory "/" sub-directory)+ output+ #:log (%make-void-port "w"))+ #t))))))+ (#f+ #f)))-- 2.19.1
Ludovic Courtès wrote on 21 Nov 2018 11:15
On tags
(address . 33432@debbugs.gnu.org)
Ludovic Courtès <ludo@gnu.org> skribis:
Toggle quote (3 lines)> When downloading over SWH, the ‘swh-download’ procedure first resolves> the tag (if it’s a tag), then tries to download the corresponding tarball
Speaking of tags, it’s not news but tags are bad from a reproducibilitystandpoint: they are mutable and per-repository. Tag lookup isnecessarily relative to a repository URL (and to a snapshot of therepository, since it can be mutated):
scheme@(guile-user)> (lookup-origin-revision "https://git.savannah.gnu.org/git/guix.git""v0.15.0") $5 = #<<revision> id: "359fdda40f754bbf1b5dc261e7427b75463b59be" date: #<date nanosecond: 0 second: 39 minute: 16 hour: 22 day: 5 month: 7 year: 2018 zone-offset: 7200> directory: "27c69c5d298a43096a53affbf881e7b13f17bdcd" directory-url: "/api/1/directory/27c69c5d298a43096a53affbf881e7b13f17bdcd/">
So if, say, SWH archived a mirror ofhttps://git.savannah.gnu.org/git/guix.git but nothttps://git.savannah.gnu.org/git/guix.git itself, then tag lookup willfail, which is sad given that the code is actually there.
To address this, possible options include:
1. Always store commit IDs rather than tags, effectively giving us “normal” Git content-addressability. This is not great for code readability and review though.
2. Store ‘sha1_git’ hashes (SHA1s of Git trees) instead of or in addition to nar sha256 hashes so we can perform lookups by content hash on SWH or Git mirrors.
#2 might be the best long-term option though it would require daemonsupport to compute, store, and check these Git-style hashes.
Ludovic Courtès wrote on 26 Nov 2018 11:11
Re: [bug#33432] [PATCH 0/2] Download Git checkouts from Software Heritage as a last resort
(address . 33432-done@debbugs.gnu.org)
Ludovic Courtès <ludo@gnu.org> skribis:
Toggle quote (3 lines)> Add (guix swh).> git-download: Download from Software Heritage as a last resort.
608d3dca89 git-download: Download from Software Heritage as a last resort. de2bfe9029 Add (guix swh).
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