support for .binder directory

docs/source/design.md

@@ -7,7 +7,7 @@ The philosophy for the repo2docker buildpacks includes:
 - using common configuration files for familiar installation and packaging tools
 - allowing configuration files to be combined to compose more complex setups
 - specifying default locations for configuration files
-(the repository's root directory or .binder directory)
+(in the repository's root, `binder` or `.binder` directory)
 
 
 When designing `repo2docker` and adding to it in the future, the

docs/source/usage.rst

@@ -75,10 +75,11 @@ Where to put configuration files
 ``repo2docker`` will look for configuration files in either:
 
 * A folder named ``binder/`` in the root of the repository.
+* A folder named ``.binder/`` in the root of the repository.
 * The root directory of the repository.
 
-If the folder ``binder/`` is located at the top level of the repository,
-only configuration files in the ``binder/`` folder will be considered.
+If either the folder ``binder/`` or ``.binder/`` is located at the top level of
+the repository, only configuration files in that folder will be considered.
 
 Check the complete list of :ref:`configuration files <config-files>` supported
 by ``repo2docker`` to see how to configure the build process.

repo2docker/buildpacks/base.py

@@ -189,6 +189,7 @@ class BuildPack:
         self.log = logging.getLogger('repo2docker')
         self.appendix = ''
         self.labels = {}
+        self._binder_dir = None
         if sys.platform.startswith('win'):
             self.log.warning("Windows environment detected. Note that Windows "
                              "support is experimental in repo2docker.")
@@ -414,12 +415,18 @@ class BuildPack:
         """
         return None
 
+    @property
+    def binder_dir(self):
+        if self._binder_dir is None:
+            for dirname in ['binder', '.binder']:
+                if os.path.exists(dirname):
+                    self._binder_dir = dirname
+            self._binder_dir = ''
+        return self._binder_dir
+
     def binder_path(self, path):
         """Locate a file"""
-        if os.path.exists('binder'):
-            return os.path.join('binder', path)
-        else:
-            return path
+        return os.path.join(self.binder_dir, path)
 
     def detect(self):
         return True

repo2docker/buildpacks/nix/nix-shell-wrapper

@@ -8,12 +8,19 @@ _term() {
 
 trap _term SIGTERM
 
+# find binder sub-directory (if present)
+for dir in "./binder" "./.binder"; do
+  if [ -e $dir ]; then
+    binder_dir = $dir
+  fi
+done
+
 # if there is a binder/ sub-directory it takes precedence
 # files outside it are ignored
-if [ -e ./binder ]; then
-  nixpath="./binder/default.nix";
-  if [ -f ./binder/start ]; then
-    chmod u+x ./binder/start
+if [ -z $binder_dir ]; then
+  nixpath="$binder_dir/default.nix";
+  if [ -f $binder_dir/start ]; then
+    chmod u+x $binder_dir/start
     # Using `$@`` here which is what the internet recommends leads to
     # errors when the command is something like `jupyter --ip=0.0.0.0 ...`
     # as nix-shell picks that up as an argument to it instead of the command.
@@ -21,7 +28,7 @@ if [ -e ./binder ]; then
     # for -- to indicate "all arguments after this are for the command, not nix-shell"
     # but it seems they have stalled/not yet produced an implementation.
     # So let's use `$*` for now.
-    nix-shell $nixpath --command "./binder/start $*" &
+    nix-shell $nixpath --command "$binder_dir/start $*" &
   else
     nix-shell $nixpath --command "$*" &
   fi

repo2docker/buildpacks/python/__init__.py

@@ -67,7 +67,7 @@ class PythonBuildPack(CondaBuildPack):
             ))
 
         # setup.py exists *and* binder dir is not used
-        if not os.path.exists('binder') and os.path.exists(setup_py):
+        if not self.binder_dir and os.path.exists(setup_py):
             assemble_scripts.append((
                 '${NB_USER}',
                 '{} install --no-cache-dir .'.format(pip)
@@ -88,6 +88,6 @@ class PythonBuildPack(CondaBuildPack):
                 return True
             else:
                 return False
-        if not os.path.exists('binder') and os.path.exists(setup_py):
+        if not self.binder_dir and os.path.exists(setup_py):
             return True
         return os.path.exists(requirements_txt)

repo2docker/buildpacks/r.py

@@ -84,7 +84,7 @@ class RBuildPack(PythonBuildPack):
             return True
 
         description_R = 'DESCRIPTION'
-        if ((not os.path.exists('binder') and os.path.exists(description_R))
+        if (not self.binder_dir and os.path.exists(description_R)
           or 'r' in self.stencila_contexts):
             if not self.checkpoint_date:
                 # no R snapshot date set through runtime.txt
@@ -300,7 +300,7 @@ class RBuildPack(PythonBuildPack):
             ]
 
         description_R = 'DESCRIPTION'
-        if not os.path.exists('binder') and os.path.exists(description_R):
+        if not self.binder_dir and os.path.exists(description_R):
             assemble_scripts += [
                 (
                     "${NB_USER}",