Document PKG_REGISTER_SHELLS framework.

Packages.txt

@@ -1,4 +1,4 @@
-# $NetBSD: Packages.txt,v 1.270 2002/11/08 09:29:14 wiz Exp $
+# $NetBSD: Packages.txt,v 1.271 2002/11/17 09:00:30 salo Exp $
 ###########################################################################
 
 			==========================
@@ -2406,6 +2406,25 @@ the installed file first and then the target file. Users will also get an
 automatic message when files are installed using this method.
 
 
+ 10.28 Packages providing login shells
+ =====================================
+
+If the purpose of the package is to provide a login shell, the variable
+PKG_SHELL should contain the full pathname of the shell executable installed
+by this package. The package Makefile also must include
+"../../mk/bsd.pkg.install.mk" prior to the inclusion of bsd.pkg.mk to use the
+automatically generated INSTALL/DEINSTALL scripts.
+
+An example taken from shells/zsh:
+
+	PKG_SHELL=	${PREFIX}/bin/zsh
+	.include "../../mk/bsd.pkg.install.mk"
+
+The shell is registered into /etc/shells file automatically in the
+post-install target by the INSTALL script generated by bsd.pkg.install.mk and
+removed in the deinstall target by the DEINSTALL script.
+
+
  11 Submitting & Committing
  ==========================