gitaly: fix libgit2 dependency

pkgs/applications/version-management/gitlab/gitaly/default.nix

@@ -20,6 +20,7 @@ let
         };
       };
   };
+
   version = "14.4.1";
   gitaly_package = "gitlab.com/gitlab-org/gitaly/v${lib.versions.major version}";
 in

pkgs/top-level/all-packages.nix

@@ -5676,7 +5676,9 @@ with pkgs;
 
   gitleaks = callPackage ../tools/security/gitleaks { };
 
-  gitaly = callPackage ../applications/version-management/gitlab/gitaly { };
+  gitaly = callPackage ../applications/version-management/gitlab/gitaly {
+    libgit2 = libgit2_1_1; # git2go only supports v1.1.x
+  };
 
   gitstats = callPackage ../applications/version-management/gitstats { };
 
@@ -16305,6 +16307,16 @@ with pkgs;
     ];
   });
 
+  libgit2_1_1 = libgit2.overrideAttrs (oldAttrs: rec {
+    version = "1.1.1";
+    src = fetchFromGitHub {
+      owner = "libgit2";
+      repo = "libgit2";
+      rev = "v${version}";
+      sha256 = "sha256-SxceIxT0aeiiiZCeSIe6EOa+MyVpQVaiv/ZZn6fkwIc=";
+    };
+  });
+
   libgit2-glib = callPackage ../development/libraries/libgit2-glib { };
 
   libhsts = callPackage ../development/libraries/libhsts { };