+# package), it should use DGIT-LIVE-DIR/dgit (etc.), or if that is
+# ENOENT, use the installed version.
+#
+# Mirror hook scripts are invoked like this:
+# MIRROR-HOOK-SCRIPT DISTRO-DIR ACTION...
+# and currently there is only one action invoked by dgit-repos-server:
+# MIRROR-HOOK-SCRIPT DISTRO-DIR updated-hook PACKAGE [...]
+#
+# Exit status of the mirror hook is advisory only. The mirror hook
+# runs too late to do anything useful about a problem, so the only
+# effect of a mirror hook exiting nonzero is a warning message to
+# stderr (which the pushing user should end up seeing).
+#
+# If the mirror hook does not exist, it is silently skipped.