add some discussion of import config limitations

Author: L0neGamer

doc/cabal-project-description-file.rst

@@ -89,8 +89,11 @@ One use case for imports is to specify a `Stackage <https://www.stackage.org/>`
 snapshot, so that your cabal project can use the same set of packages as
 that snapshot. To use the ``lts-21.25`` resolver, you can write
 ``import: https://www.stackage.org/lts-21.25/cabal.config`` in your
-``cabal.project``. Note that Stackage does not guarantee that these will work
-with regards to revisions.
+``cabal.project``.
+
+There are a number of limitations that come with this approach however; please
+see :ref:`How can I have a reproducible set of versions for my dependencies?<how reproducible>` for
+more information.
 
 Specifying the local packages
 -----------------------------

doc/nix-local-build.rst

@@ -104,6 +104,8 @@ for each package using :cfg-field:`profiling-detail`::
 Alternately, you can call ``cabal build --enable-profiling`` to
 temporarily build with profiling.
 
+.. _how reproducible:
+
 How can I have a reproducible set of versions for my dependencies?
 ------------------------------------------------------------------
 
@@ -134,6 +136,17 @@ development environments.
 .. _Stackage: https://stackage.org/
 .. _versions of packages in lts-19.2: https://www.stackage.org/lts-19.2
 
+Limitations
+^^^^^^^^^^^
+
+Stackage does not guarantee that the config files will work with revisions, and
+it's not currently possible to `override used versions of packages <https://github.com/haskell/cabal/issues/9511>`
+or to `specify revisions <https://github.com/haskell/cabal/issues/7833>` using
+cabal.
+
+To mitigate these shortcomings, you can download the config file that is linked
+to and remove the troublesome constraints.
+
 How it works
 ============