rev-parse: have --parseopt callers exit 0 on --help

The standard philosophy for Unix software when a help option (such as --help) is specified is that the software should exit 0, printing the help output to standard output, since the standard output is for user-requested output and the program performed the requested task successfully. If the user specifies an incorrect option, then the help output should be printed to standard error (since the user has made a mistake) and it should exit unsuccessfully. git rev-parse --parseopt properly directs the output in both of these cases, but it currently exits 129 when it receives a --help or -h option on the command line, which causes its invoking script to do the same. This is not in line with the usual behavior and it causes scripts using this command to exit unsuccessfully on --help as well. Note that Git subcommands implemented using scripts, such as git submodule, don't have this problem because Git itself intercepts the --help option and runs man (or a similar tool), which then exits 0. However, this still affects the myriad scripts that use this functionality because Git is widespread and the --parseopt functionality is a good way to get sensible option parsing across shells in a portable way. Because git rev-parse --parseopt is intended to be eval'd by the shell, when help output is to be printed to standard output, Git actually prints a cat command with a heredoc since the standard output is being evaluated by the shell. Thus, to do the right thing, simply add an "exit 0" right after the end of the heredoc, which will cause the invoking program to exit successfully. The usual invocation recommended by the manual page is this: eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)" Thus, the fact that git rev-parse --parseopt still exits 129 in this case is irrelevant, since the "echo exit $?" will print "exit 129", but that will be after the "exit 0" printed by Git—and thus ignored, since the shell will have already exited successfully. Update the tests for this case. Note that we no longer need to delete only the first and last lines in some tests, so add a command to delete the end of the heredoc as well. We could do something clever with sed to delete all but the last two lines or switch to head and tail, but those would be more complicated and less readable, so just stick with the simple approach. In t1517, add three shell scripts to the failure case because they no longer return 129 as expected. In a future commit, we'll change the expected result to exit 0 and these will become successful again. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>