fix R DESCRIPTION installation

docs/source/config_files.rst

@@ -109,6 +109,17 @@ While one can specify dependencies in ``setup.py``,
 repo2docker **requires configuration files such as** ``environment.yml`` or
 ``requirements.txt`` to install dependencies during the build process.
 
+``DESCRIPTION``
+~~~~~~~~~~~~~~~
+
+To install your repository like an R package, you may include a
+``DESCRIPTION`` file. repo2docker installs the package and dependencies
+ from the ``DESCRIPTION`` by running ``devtools:install_git(".")``.
+
+ You also need to have a ``runtime.txt`` file that is formatted as
+ ``r-<YYYY>-<MM>-<DD>``, where YYYY-MM-DD is a snapshot at MRAN that will be
+ used for your R installation.
+
 .. _postBuild:
 
 ``postBuild``

repo2docker/buildpacks/r.py

@@ -263,8 +263,7 @@ class RBuildPack(PythonBuildPack):
                 (
                     "${NB_USER}",
                     r"""
-                    R CMD build . && \
+                    R --quiet -e "devtools::install_git('.')"
-                    R CMD install .
                     """
                 )
             ]

tests/external/reproductions.repos.yaml

@@ -30,3 +30,7 @@
   url: https://github.com/QuantStack/xeus-cling
   ref: 0.4.5
   verify: jupyter kernelspec list
+- name: Test compiling R package
+  url: https://github.com/gedankenstuecke/binder-r-description
+  ref: master
+  verify: R --quiet -e 'binderdescription::print_something()'