[packages] Update module documentation

src/modules/packages/packages.conf

@@ -29,9 +29,10 @@ update_db: true
 # packages that need to be installed or removed can run before
 # this one. Distro developers may want to install locale packages
 # or remove drivers not needed on the installed system.
-# This job will populate a list of dictionaries in the global
-# storage called "packageOperations" and it is processed
-# after the static list in the job configuration.
+# Such a job would populate a list of dictionaries in the global
+# storage called "packageOperations" and that list is processed
+# after the static list in the job configuration (i.e. the list
+# that is in this configuration file).
 #
 # Allowed package operations are:
 #  - install, try_install: will call the package manager to
@@ -49,7 +50,7 @@ update_db: true
 #       while try_remove carries on. Packages may be listed as
 #       (localized) names.
 #
-# There are two formats for naming packages: as a name # or as package-data,
+# There are two formats for naming packages: as a name or as package-data,
 # which is an object notation providing package-name, as well as pre- and
 # post-install scripts.
 #
@@ -74,15 +75,16 @@ update_db: true
 #
 # - if the system locale is English (generally US English; en_GB is a valid
 #   localization), then the package is not installed at all,
-# - otherwise LOCALE is replaced by the Bcp47 name of the selected system
-#   locale, e.g. nl_BE.
+# - otherwise $LOCALE or ${LOCALE} is replaced by the Bcp47 name of the selected
+#   system locale, e.g. nl_BE. Note that just plain LOCALE will not be replaced,
+#   so foo-LOCALE will be unchanged, while foo-$LOCALE will be changed.
 #
 # The following installs localizations for vi, if they are relevant; if
 # there is no localization, installation continues normally.
 #
 # - install
-#   - vi-LOCALE
-#   - package: vi-LOCALE
+#   - vi-$LOCALE
+#   - package: vi-${LOCALE}
 #     pre-script: touch /tmp/installing-vi
 #     post-script: rm -f /tmp/installing-vi
 #