Fixed help of Diff and ShowCommands commands

jgit.sh <command> --help was not working for the commands Diff
and ShowCommands because of missing metaVar information. Missing
information is added here.

Change-Id: I0ab7e35006b6aa7d4326a634309dddfcdb78f2a6
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
3 files changed