git-download: Move fallback code to (guix build git).

* guix/build/git.scm (git-fetch-with-fallback): New procedure, with code
taken from…
* guix/git-download.scm (git-fetch): … here.
[modules]: Remove modules that are no longer directly used in ‘build’.
[build]: Use ‘git-fetch-with-fallback’.

2 files changed, 50 insertions, 41 deletions

diff --git a/guix/build/git.scm b/guix/build/git.scm
index deda10fee8..0ff263c81b 100644
--- a/guix/build/git.scm
+++ b/guix/build/git.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2016, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2016, 2019, 2023 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,9 +18,12 @@
 
 (define-module (guix build git)
   #:use-module (guix build utils)
+  #:autoload   (guix build download-nar) (download-nar)
+  #:autoload   (guix swh) (%verify-swh-certificate? swh-download)
   #:use-module (srfi srfi-34)
   #:use-module (ice-9 format)
-  #:export (git-fetch))
+  #:export (git-fetch
+            git-fetch-with-fallback))
 
 ;;; Commentary:
 ;;;
@@ -76,4 +79,41 @@ recursively.  Return #t on success, #f otherwise."
       (delete-file-recursively ".git")
       #t)))
 
+
+(define* (git-fetch-with-fallback url commit directory
+                                  #:key (git-command "git") recursive?)
+  "Like 'git-fetch', fetch COMMIT from URL into DIRECTORY, but fall back to
+alternative methods when fetching from URL fails: attempt to download a nar,
+and if that also fails, download from the Software Heritage archive."
+  (or (git-fetch url commit directory
+                 #:recursive? recursive?
+                 #:git-command git-command)
+      (download-nar directory)
+
+      ;; As a last resort, attempt to download from Software Heritage.
+      ;; Disable X.509 certificate verification to avoid depending
+      ;; on nss-certs--we're authenticating the checkout anyway.
+      ;; XXX: Currently recursive checkouts are not supported.
+      (and (not recursive?)
+           (parameterize ((%verify-swh-certificate? #f))
+             (format (current-error-port)
+                     "Trying to download from Software Heritage...~%")
+
+             (swh-download url commit directory)
+             (when (file-exists?
+                    (string-append directory "/.gitattributes"))
+               ;; Perform CR/LF conversion and other changes
+               ;; specificied by '.gitattributes'.
+               (invoke git-command "-C" directory "init")
+               (invoke git-command "-C" directory "config" "--local"
+                       "user.email" "you@example.org")
+               (invoke git-command "-C" directory "config" "--local"
+                       "user.name" "Your Name")
+               (invoke git-command "-C" directory "add" ".")
+               (invoke git-command "-C" directory "commit" "-am" "init")
+               (invoke git-command "-C" directory "read-tree" "--empty")
+               (invoke git-command "-C" directory "reset" "--hard")
+               (delete-file-recursively
+                (string-append directory "/.git")))))))
+
 ;;; git.scm ends here
diff --git a/guix/git-download.scm b/guix/git-download.scm
index d88f4c40ee..8989b1b463 100644
--- a/guix/git-download.scm
+++ b/guix/git-download.scm
@@ -116,19 +116,16 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
   (define modules
     (delete '(guix config)
             (source-module-closure '((guix build git)
-                                     (guix build utils)
-                                     (guix build download-nar)
-                                     (guix swh)))))
+                                     (guix build utils)))))
 
   (define build
     (with-imported-modules modules
-      (with-extensions (list guile-json gnutls   ;for (guix swh)
+      (with-extensions (list guile-json gnutls    ;for (guix swh)
                              guile-lzlib)
         #~(begin
             (use-modules (guix build git)
-                         (guix build utils)
-                         (guix build download-nar)
-                         (guix swh)
+                         ((guix build utils)
+                          #:select (set-path-environment-variable))
                          (ice-9 match))
 
             (define recursive?
@@ -151,38 +148,10 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
             (setvbuf (current-output-port) 'line)
             (setvbuf (current-error-port) 'line)
 
-            (or (git-fetch (getenv "git url") (getenv "git commit")
-                           #$output
-                           #:recursive? recursive?
-                           #:git-command "git")
-                (download-nar #$output)
-
-                ;; As a last resort, attempt to download from Software Heritage.
-                ;; Disable X.509 certificate verification to avoid depending
-                ;; on nss-certs--we're authenticating the checkout anyway.
-                ;; XXX: Currently recursive checkouts are not supported.
-                (and (not recursive?)
-                     (parameterize ((%verify-swh-certificate? #f))
-                       (format (current-error-port)
-                               "Trying to download from Software Heritage...~%")
-
-                       (swh-download (getenv "git url") (getenv "git commit")
-                                     #$output)
-                       (when (file-exists?
-                              (string-append #$output "/.gitattributes"))
-                         ;; Perform CR/LF conversion and other changes
-                         ;; specificied by '.gitattributes'.
-                         (invoke "git" "-C" #$output "init")
-                         (invoke "git" "-C" #$output "config" "--local"
-                                 "user.email" "you@example.org")
-                         (invoke "git" "-C" #$output "config" "--local"
-                                 "user.name" "Your Name")
-                         (invoke "git" "-C" #$output "add" ".")
-                         (invoke "git" "-C" #$output "commit" "-am" "init")
-                         (invoke "git" "-C" #$output "read-tree" "--empty")
-                         (invoke "git" "-C" #$output "reset" "--hard")
-                         (delete-file-recursively
-                          (string-append #$output "/.git"))))))))))
+            (git-fetch-with-fallback (getenv "git url") (getenv "git commit")
+                                     #$output
+                                     #:recursive? recursive?
+                                     #:git-command "git")))))
 
   (mlet %store-monad ((guile (package->derivation guile system)))
     (gexp->derivation (or name "git-checkout") build