feat(nix): reuse nixpkgs definition with overrides

Reuse nixpkgs definition for git-branchless, and supply local changes
through overrides. This ensures that nixpkgs updates are automatically
propagated to the package definition here.

In flake.nix we recommend people to contribute to nixpkgs first for it
to be the primary source of package definition; and then pull the
changes down here by updating flake.lock.

Author: bryango

flake.nix

@@ -15,57 +15,27 @@
     in
     {
       overlays.default = (final: prev: {
-        git-branchless = final.callPackage
-          (
-            { lib
-            , git
-            , libiconv
-            , ncurses
-            , openssl
-            , pkg-config
-            , rustPlatform
-            , sqlite
-            , stdenv
-            , Security
-            , SystemConfiguration
-            }:
-
-            rustPlatform.buildRustPackage {
-              name = "git-branchless";
 
-              src = self;
-
-              cargoLock = {
-                lockFile = "${self}/Cargo.lock";
-              };
-
-              nativeBuildInputs = [ pkg-config ];
+        # reuse the definition from nixpkgs git-branchless
+        git-branchless = prev.git-branchless.overrideAttrs ({ meta, ... }: {
+          name = "git-branchless";
+          src = self;
+          cargoDeps = final.rustPlatform.importCargoLock {
+            lockFile = ./Cargo.lock;
+          };
 
-              buildInputs = [
-                ncurses
-                openssl
-                sqlite
-              ] ++ lib.optionals stdenv.isDarwin [
-                Security
-                SystemConfiguration
-                libiconv
-              ];
+          # for `flake.nix` contributors: put additional local overrides here.
+          # if the changes are also applicable to the `git-branchless` package
+          # in nixpkgs, consider first improving the definition there, and then
+          # update the `flake.lock` here.
 
-              preCheck = ''
-                export TEST_GIT=${git}/bin/git
-                export TEST_GIT_EXEC_PATH=$(${git}/bin/git --exec-path)
-              '';
-              # FIXME: these tests time out when run in the Nix sandbox
-              checkFlags = [
-                "--skip=test_switch_pty"
-                "--skip=test_next_ambiguous_interactive"
-                "--skip=test_switch_auto_switch_interactive"
-              ];
-            }
-          )
-          {
-            inherit (final.darwin.apple_sdk.frameworks) Security SystemConfiguration;
+          # in case local overrides might confuse upstream maintainers,
+          # we do not list them here:
+          meta = (removeAttrs meta [ "maintainers" ]) // {
+            # to correctly generate meta.position for back trace:
+            inherit (meta) description;
           };
+        });
 
         scm-diff-editor = final.callPackage
           (