Merge pull request #2503 from rear/new_036_valid_output_methods_scrip…

…t_issue2501

New 036_valid_output_methods.sh to error out for unsupported OUTPUT methods:
For "rear mkbackup/mkrescue/mkbackuponly/mkopalpba"
(i.e. for all workflows that run the 'prep' stage)
check that the OUTPUT method is actually implemented
i.e. check that a usr/share/rear/output/$OUTPUT directory exists
and error out when an OUTPUT method seems to be not supported
to ensure that the user cannot specify a non-working OUTPUT in etc/rear/local.conf
(cf. usr/share/rear/prep/default/035_valid_backup_methods.sh)
see #2501

usr/share/rear/prep/default/036_valid_output_methods.sh

@@ -0,0 +1,13 @@
+
+# For "rear mkbackup/mkrescue/mkbackuponly/mkopalpba"
+# (i.e. for all workflows that run the 'prep' stage)
+# check that the OUTPUT method is actually implemented
+# i.e. check that a usr/share/rear/output/$OUTPUT directory exists
+# and error out when an OUTPUT method seems to be not supported
+# to ensure that the user cannot specify a non-working OUTPUT in /etc/rear/local.conf
+# see https://github.com/rear/rear/issues/2501
+# and cf. usr/share/rear/prep/default/035_valid_backup_methods.sh
+
+if ! test -d "$SHARE_DIR/output/$OUTPUT" ; then
+    Error "The OUTPUT method '$OUTPUT' is not supported (no $SHARE_DIR/output/$OUTPUT directory)"
+fi