Add pre-remove and post-remove hooks to dss.ggo.

These are not yet used in the code.

diff --git a/dss.ggo b/dss.ggo
index 099df4cd163765da66e2ba7eb1dca26789af1ed4..9c687f42d575606cdb852bf7b829e4def7d64edf 100644 (file)
--- a/dss.ggo
+++ b/dss.ggo
@@ -277,6 +277,37 @@ details="
        store them in a database for further analysis.
 "
 
+option "pre-remove-hook" -
+#~~~~~~~~~~~~~~~~~~~~~~~~~~
+"Executed before snapshot removal"
+string typestr="command"
+optional
+details="
+       Execute this command before removing a snapshot. If this
+       command returns with a non-zero exit status, no snapshot is
+       being removed and the operation is retried later.
+
+       For example, one might want to execute a script that checks
+       whether the snapshot to be deleted is currently used by
+       another process, e.g. by a tape-based backup system that runs
+       concurrently to dss.
+
+       Another possible application of this is to record disk-usage
+       patterns before and after snapshot removal.
+"
+
+option "post-remove-hook" -
+#~~~~~~~~~~~~~~~~~~~~~~~~~~
+"Executed after snapshot removal"
+string typestr="command"
+optional
+details="
+       Execute this after a snapshot has successfully been
+       removed. The full path of the removed snapshot is
+       passed to the hook as the first argument. The exit code of
+       this hook is ignored.
+"
+
 option "exit-hook" e
 #~~~~~~~~~~~~~~~~~~~
 "Executed if run command exits"