dpkg-source: Document --before-build and --after-build in --help output

debian/changelog

@@ -3,6 +3,7 @@ dpkg (1.18.23) UNRELEASED; urgency=medium
   * Documentation:
     - Clarify the requirements for deb-conffile(5) pathnames. Closes: #854417
       Proposed by Dieter Adriaenssens <dieter.adriaenssens@gmail.com>.
+    - Document dpkg-source --before-build and --after-build in --help output.
 
  -- Guillem Jover <guillem@debian.org>  Wed, 01 Feb 2017 06:28:28 +0100
 

scripts/dpkg-source.pl

@@ -620,6 +620,8 @@ sub usage {
                            extract source package.
   -b, --build <dir>        build source package.
       --print-format <dir> print the format to be used for the source package.
+      --before-build <dir> run the corresponding source package format hook.
+      --after-build <dir>  run the corresponding source package format hook.
       --commit [<dir> [<patch-name>]]
                            store upstream changes in a new patch.')
     . "\n\n" . g_(