[Rd] Small Extension to license()/licence()

[R. Michael Weylandt]

By analogy with maintainer(), I suggest extending license() to give
the licensing terms of packages as well as R itself when prompted.
Below is a small patch in that direction. This won't break anything
and imposes no significant maintenance burden; it has the advantage of
making it ever so marginally easier to know package licenses.

Given the existence of license forms like GPL >=2, I don't see a easy
programmatic way of identifying what RShowDoc() can provide and what
it can't, so I've left that out.

Cheers,

Michael

-------------------------------------------------

Index: src/library/base/R/license.R
===================================================================
--- src/library/base/R/license.R	(revision 60839)
+++ src/library/base/R/license.R	(working copy)
@@ -16,8 +16,14 @@
 #  A copy of the GNU General Public License is available at
 #  http://www.r-project.org/Licenses/

-licence <- license <- function() {
-    cat("\nThis software is distributed under the terms of the GNU General\n")
+licence <- license <- function(pkg = NULL) {
+  if(!is.null(pkg)) pkgd <- packageDescription(pkg)
+  if(is.null(pkg) || pkgd[["Priority"]] == "base"){
+    if(is.null(pkg)){
+      cat("\nThis software is distributed under the terms of the GNU
General\n")
+    } else {
+      cat(pkg, "is part of R and distributed under the terms of the
GNU General\n")
+    }
     cat("Public License, either Version 2, June 1991 or Version 3,
June 2007.\n")
     cat("The terms of version 2 of the license are in a file called
COPYING\nwhich you should have received with\n")
     cat("this software and which can be displayed by RShowDoc(\"COPYING\").\n")
@@ -34,4 +40,9 @@
     cat("Version 3 of the license can be displayed by RShowDoc(\"LGPL-3\").\n")
     cat("\n")
     cat("'Share and Enjoy.'\n\n")
+  } else {
+    cat(pkg, "is distributed under the", pkgd[["License"]],"License.\n")
+  }
+
+  invisible(NULL)
 }
Index: src/library/base/man/license.Rd
===================================================================
--- src/library/base/man/license.Rd	(revision 60839)
+++ src/library/base/man/license.Rd	(working copy)
@@ -8,13 +8,18 @@
 \alias{license}
 \alias{licence}
 \description{
-  The license terms under which \R is distributed.
+  The license terms under which \R or a contributed package is distributed.
 }
 \usage{
-license()
-licence()
+license(pkg = NULL)
+licence(pkg = NULL)
 }
 \details{
+  If pkg is "NULL", the licensing terms of R are given; else, the
+  license of the package (as taken from the package DESCRIPTION file) is
+  returned. Major open-source licenses can be found in
+  \file{\var{\link{R_HOME}}/share/licenses} and viewed with \link{RShowDoc}.
+
   \R is distributed under the terms of the GNU GENERAL PUBLIC LICENSE,
   either Version 2, June 1991 or Version 3, June 2007.  A copy of the
   version 2 license is in file \file{\var{\link{R_HOME}}/COPYING} and