libgit2: use upstream version if possible

we don't seem to use libgit2 for fetching via ssh, hence it shouldn't
matter if it's using libssh or the ssh binary.

(cherry picked from commit 0b61b758fb)

packaging/dependencies.nix

@@ -65,39 +65,37 @@ scope: {
         installPhase = lib.replaceStrings [ "--without-python" ] [ "" ] old.installPhase;
       });
 
-  libgit2 = pkgs.libgit2.overrideAttrs (
-    attrs:
-    {
-      cmakeFlags = attrs.cmakeFlags or [ ] ++ [ "-DUSE_SSH=exec" ];
-    }
-    # libgit2: Nixpkgs 24.11 has < 1.9.0, which needs our patches
-    // lib.optionalAttrs (!lib.versionAtLeast pkgs.libgit2.version "1.9.0") {
-      nativeBuildInputs =
-        attrs.nativeBuildInputs or [ ]
-        # gitMinimal does not build on Windows. See packbuilder patch.
-        ++ lib.optionals (!stdenv.hostPlatform.isWindows) [
-          # Needed for `git apply`; see `prePatch`
-          pkgs.buildPackages.gitMinimal
-        ];
-      # Only `git apply` can handle git binary patches
-      prePatch =
-        attrs.prePatch or ""
-        + lib.optionalString (!stdenv.hostPlatform.isWindows) ''
-          patch() {
-            git apply
-          }
-        '';
-      patches =
-        attrs.patches or [ ]
-        ++ [
-          ./patches/libgit2-mempack-thin-packfile.patch
-        ]
-        # gitMinimal does not build on Windows, but fortunately this patch only
-        # impacts interruptibility
-        ++ lib.optionals (!stdenv.hostPlatform.isWindows) [
-          # binary patch; see `prePatch`
-          ./patches/libgit2-packbuilder-callback-interruptible.patch
-        ];
-    }
-  );
+  libgit2 =
+    if lib.versionAtLeast pkgs.libgit2.version "1.9.0" then
+      pkgs.libgit2
+    else
+      pkgs.libgit2.overrideAttrs (attrs: {
+        # libgit2: Nixpkgs 24.11 has < 1.9.0, which needs our patches
+        nativeBuildInputs =
+          attrs.nativeBuildInputs or [ ]
+          # gitMinimal does not build on Windows. See packbuilder patch.
+          ++ lib.optionals (!stdenv.hostPlatform.isWindows) [
+            # Needed for `git apply`; see `prePatch`
+            pkgs.buildPackages.gitMinimal
+          ];
+        # Only `git apply` can handle git binary patches
+        prePatch =
+          attrs.prePatch or ""
+          + lib.optionalString (!stdenv.hostPlatform.isWindows) ''
+            patch() {
+              git apply
+            }
+          '';
+        patches =
+          attrs.patches or [ ]
+          ++ [
+            ./patches/libgit2-mempack-thin-packfile.patch
+          ]
+          # gitMinimal does not build on Windows, but fortunately this patch only
+          # impacts interruptibility
+          ++ lib.optionals (!stdenv.hostPlatform.isWindows) [
+            # binary patch; see `prePatch`
+            ./patches/libgit2-packbuilder-callback-interruptible.patch
+          ];
+      });
 }