Make git-based deps check out all submodules

CHANGELOG.md

@@ -4,6 +4,11 @@
     `tzdata` packages in `nix/build-support/stacklock2nix/suggestedOverlay.nix`.
     Fixed in [#52](https://github.com/cdepillabout/stacklock2nix/pull/52).
 
+*   Make sure Haskell packages specified as Git repos in the `stack.yaml` file
+    check out all submodules when fetching their source.
+    Fixed in [#53](https://github.com/cdepillabout/stacklock2nix/pull/53).
+    Thanks to [@isomorpheme](https://github.com/isomorpheme) for reporting this.
+
 ## 4.0.2
 
 *   Fix a bug where `stacklock2nix` would throw an error if there were

nix/build-support/stacklock2nix/default.nix

@@ -382,7 +382,15 @@ let
             url = haskPkgLock.git;
             name = srcName;
             rev = haskPkgLock.commit;
+
+            # We make sure that ALL Git refs are fetched, since the user may be
+            # using a commit on a branch that is not reachable from the default branch
+            # (usually `master` / `main`).  This is what `stack` does by default.
             allRefs = true;
+
+            # We make sure that all submodules are checked out, since `stack`
+            # does this by default.
+            submodules = true;
           };
           src =
             if haskPkgLock ? "subdir" then