gnu: libgit2: Fix Clar test framework.

This commit reverts 'patch' hack introduced in
a48a1071a6 and fixes bug in the Clar test
framework.

Patch is proposed to Clar upstream as
<https://github.com/vmg/clar/pull/78>.

* gnu/local.mk: Add libgit2-0.25.1-mtime-0.patch.
* gnu/packages/patches/libgit2-0.25.1-mtime-0.patch: New file.
* gnu/packages/version-control.scm (libgit2)[arguments]:
Remove 'apply-patch' phase.
[inputs]: Remove "patch".
[source]: Add 'patches' field.

Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/local.mk

@@ -729,6 +729,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libevent-2.1-dns-tests.patch		\
   %D%/packages/patches/libevent-2.1-skip-failing-test.patch	\
   %D%/packages/patches/libextractor-ffmpeg-3.patch		\
+  %D%/packages/patches/libgit2-0.25.1-mtime-0.patch		\
   %D%/packages/patches/libgit2-use-after-free.patch		\
   %D%/packages/patches/libjxr-fix-function-signature.patch	\
   %D%/packages/patches/libjxr-fix-typos.patch			\

gnu/packages/patches/libgit2-0.25.1-mtime-0.patch

@@ -0,0 +1,14 @@
+The Clar test framework has a bug whereby it skips the parsing phase
+on files with mtime=0.
+
+Reported upstream at <https://github.com/vmg/clar/pull/78>.
+
+diff --git a/tests/generate.py b/tests/generate.py
+index b639c8f..111ca41 100644
+--- a/tests/generate.py
++++ b/tests/generate.py
+@@ -63,3 +63,3 @@ class Module(object):
+ 
+-        self.mtime = 0
++        self.mtime = None # Guix sets all file mtimes to '0'
+         self.enabled = True

gnu/packages/version-control.scm

@@ -336,7 +336,9 @@ everything from small to very large projects with speed and efficiency.")
               (file-name (string-append name "-" version ".tar.gz"))
               (sha256
                (base32
-                "1cdwcw38frc1wf28x5ppddazv9hywc718j92f3xa3ybzzycyds3s"))))
+                "1cdwcw38frc1wf28x5ppddazv9hywc718j92f3xa3ybzzycyds3s"))
+              (patches (search-patches "libgit2-use-after-free.patch"
+                                       "libgit2-0.25.1-mtime-0.patch"))))
     (build-system cmake-build-system)
     (arguments
      `(#:phases
@@ -349,25 +351,13 @@ everything from small to very large projects with speed and efficiency.")
                (("/bin/cp") (which "cp"))
                (("/bin/rm") (which "rm")))
              #t))
-         (add-after 'unpack 'apply-patch
-           (lambda* (#:key inputs #:allow-other-keys)
-             ;; XXX: For some reason adding the patch in 'patches', which
-             ;; leads to a new tarball with all timestamps reset and ordering
-             ;; by name (slightly different file order compared to the
-             ;; original tarball) leads to an obscure Python error while
-             ;; running 'generate.py':
-             ;;   'Module' object has no attribute 'callbacks'
-             ;; Thus, apply the patch here, which minimizes disruption.
-             (let ((patch (assoc-ref inputs "patch")))
-               (zero? (system* "patch" "-p1" "--force" "--input" patch)))))
          ;; Run checks more verbosely.
          (replace 'check
            (lambda _ (zero? (system* "./libgit2_clar" "-v" "-Q")))))))
     (inputs
      `(("libssh2" ,libssh2)
        ("libcurl" ,curl)
-       ("python" ,python-wrapper)
-       ("patch" ,(search-patch "libgit2-use-after-free.patch"))))
+       ("python" ,python-wrapper)))
     (native-inputs
      `(("pkg-config" ,pkg-config)))
     (propagated-inputs