Add the "essential" var for use in templates.

This will be used to mark packages that shouldn't be
removed if it's being updated, e.g libc.

--HG--
extra : convert_revision : bba7d14b2d112edaf17e6adc04a222a3d663da34

shutils/metadata.sh

@@ -60,7 +60,7 @@ xbps_write_metadata_pkg()
 			msg_error "Cannot find subpackage template!"
 		fi
 		unset run_depends conf_files keep_dirs noarch triggers \
-			revision openrc_services
+			revision openrc_services essential
 		. $XBPS_TEMPLATESDIR/${sourcepkg}/${subpkg}.template
 		pkgname=${sourcepkg}-${subpkg}
 		set_tmpl_common_vars
@@ -289,6 +289,12 @@ _EOF
 		Add_dependency run OpenRC
 	fi
 
+	# Is this an essential pkg?
+	if [ -n "$essential" ]; then
+		echo "<key>essential</key>" >> $TMPFPROPS
+		echo "<true/>" >> $TMPFPROPS
+	fi
+
 	# Dependencies
 	if [ -n "$run_depends" ]; then
 		echo "<key>run_depends</key>" >> $TMPFPROPS

shutils/tmpl_funcs.sh

@@ -66,7 +66,7 @@ reset_tmpl_vars()
 			make_build_target configure_script noextract \
 			pre_configure pre_build pre_install configure_shell \
 			post_configure post_build post_install \
-			make_install_target version revision \
+			make_install_target version revision essential \
 			sgml_catalogs xml_catalogs xml_entries sgml_entries \
 			build_depends libtool_fixup_la_stage no_fixup_libtool \
 			disable_parallel_build run_depends cross_compiler \