Avoid hardlinks when cloning across filesystems

Would be nice if git detected this for us, but sadly it doesn't.

package.inc.sh

@@ -156,20 +156,28 @@ package_export() {
 }
 
 package_checkout() {
-  local remote
+  local remote clone_args
   pkgname=$1
 
   package_init "$pkgname" remote || return
 
   git show-ref -q "refs/heads/$remote/packages/$pkgname" ||
       git branch -qf --no-track {,}"$remote/packages/$pkgname"
 
-  quiet_git clone \
-    --local \
-    --single-branch \
-    --branch "$remote/packages/$pkgname" \
-    --config "pull.rebase=true" \
-    "$ASPROOT" "$pkgname" || return
+  clone_args=(
+    --local
+    --single-branch
+    --branch "$remote/packages/$pkgname"
+    --config "pull.rebase=true"
+  )
+
+  # If the current directory isn't on the same FS as us, then we can't use
+  # hardlinks in the clone, implied by --local.
+  if [[ $(stat -c %d "$ASPROOT") != "$(stat -c %d .)" ]] ; then
+    clone_args+=(--no-hardlinks)
+  fi
+
+  quiet_git clone "${clone_args[@]}" "$ASPROOT" "$pkgname"
 }
 
 package_get_repos_with_arch() {