Add description of rcmd notes

.Rbuildignore

@@ -2,3 +2,4 @@
 ^\.Rproj\.user$
 ^\.travis\.yml$
 ^NEWS.md$
+^rcmd-notes.md$

rcmd-notes.md

@@ -0,0 +1,25 @@
+* checking dependencies in R code ... NOTE
+  Missing or unexported object: ‘roxygen2::clear_caches’
+  See the information on DESCRIPTION files in the chapter ‘Creating R
+  packages’ of the ‘Writing R Extensions’ manual.
+
+  checking R code for possible problems ... NOTE
+  document_roxygen2: no visible binding for global variable ‘parse.file’
+
+  Or similar: devtools now conditionally supports two versions of roxygen2, 
+  so some functions aren't found and some arguments don't match
+
+* checking R code for possible problems ... NOTE
+  Found the following calls to attach():
+    File ‘devtools/R/package-env.r’:
+    attach(NULL, name = pkg_env_name(pkg))
+
+  This is needed because devtools simulated package loading, and hence
+  needs to attach environments to the search path.
+
+* There are ::: calls to the package's namespace in its code. A package
+  almost never needs to use ::: for its own objects:  ‘run_example’
+
+  This is needed because that function actually generates an external
+  file that is run in a fresh R session.
+