Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/tests/lang/eval-okay-string.nix

@@ -0,0 +1,12 @@
+"foo" + "bar"
+  + toString (/a/b + /c/d)
+  + toString (/foo/bar + "/../xyzzy/." + "/foo.txt")
+  + ("/../foo" + toString /x/y)
+  + "escape: \"quote\" \n \\"
+  + "end
+of
+line"
+  + "foo${if true then "b${"a" + "r"}" else "xyzzy"}blaat"
+  + "foo$bar"
+  + "$\"$\""
+  + "$"