Use a single setting for disabling API doc build

docs/README.md

@@ -33,4 +33,4 @@ Similarly, you can build just the PySpark epydoc by running `epydoc --config epy
 
 When you run `jekyll` in the docs directory, it will also copy over the scaladoc for the various Spark subprojects into the docs directory (and then also into the _site directory). We use a jekyll plugin to run `sbt/sbt doc` before building the site so if you haven't run it (recently) it may take some time as it generates all of the scaladoc.  The jekyll plugin also generates the PySpark docs using [epydoc](http://epydoc.sourceforge.net/).
 
-NOTE: To skip the step of building and copying over the scaladoc when you build the docs, run `SKIP_SCALADOC=1 jekyll`.  Similarly, `SKIP_EPYDOC=1 jekyll` will skip PySpark API doc generation.
+NOTE: To skip the step of building and copying over the Scala and Python API docs, run `SKIP_API=1 jekyll`.

docs/_plugins/copy_api_dirs.rb

@@ -1,7 +1,8 @@
 require 'fileutils'
 include FileUtils
 
-if ENV['SKIP_SCALADOC'] != '1'
+if ENV['SKIP_API'] != '1'
+  # Build Scaladoc for Java/Scala
   projects = ["core", "examples", "repl", "bagel", "streaming"]
 
   puts "Moving to project root and building scaladoc."
@@ -27,9 +28,8 @@ if ENV['SKIP_SCALADOC'] != '1'
     puts "cp -r " + source + "/. " + dest
     cp_r(source + "/.", dest)
   end
-end
 
-if ENV['SKIP_EPYDOC'] != '1'
+  # Build Epydoc for Python
   puts "Moving to python directory and building epydoc."
   cd("../python")
   puts `epydoc --config epydoc.conf`