Add "no command line variant" of src-repo-pkg

doc/cabal-project-description-file.rst

@@ -216,6 +216,14 @@ consider during package retrieval. This allows use of a package from a
 remote version control system, rather than looking for that package in
 Hackage.
 
+Since version 3.4, cabal-install creates tarballs for each package coming from a
+``source-repository-package`` stanza (effectively applying cabal sdists to such
+packages). It gathers the names of the packages from the appropriate ``.cabal``
+file in the version control repository, and allows their use just like Hackage
+or locally defined packages.
+
+There is no command line variant of this stanza.
+
 .. code-block:: cabal
 
     packages: .
@@ -237,12 +245,6 @@ Hackage.
         tag: e76fdc753e660dfa615af6c8b6a2ad9ddf6afe70
         post-checkout-command: autoreconf -i
 
-Since version 3.4, cabal-install creates tarballs for each package coming
-from a ``source-repository-package`` stanza (effectively applying cabal
-sdists to such packages). It gathers the names of the packages from the
-appropriate ``.cabal`` file in the version control repository, and allows
-their use just like Hackage or locally defined packages.
-
 .. _source-repository-package-fields:
 
 The :ref:`VCS fields<vcs-fields>` of ``source-repository-package`` are: