Merge branch 'bc/parse-options-exit-0-on-help' into next

Option parsing with 'git rev-parse --parseopt' and in most 'git' subcommands has been updated to exit with 0 (instead of 129) when the help option ('-h' or '--help') is requested directly by the user, aligning with standard Unix convention. * bc/parse-options-exit-0-on-help: parse-options: exit 0 on -h rev-parse: have --parseopt callers exit 0 on --help parse-options: add a separate case for help output on error t1517: skip svn tests if svn is not installed