RFR: 323: ArgumentParser should support --version

[Erik Helin]

Hi all,

please review this patch that makes the CLI tools **not** show an error when required flags and inputs are missing _and_ the flag `--version` is specified. If a user runs `git <tool> --version` then they shouldn't have to add required flags or input, they just want to see the version.

Testing:
- [x] Manual testing on Linux x64

Thanks,
Erik

-------------

Commit messages:
 - cli: skip required flags for --version

Changes: https://git.openjdk.java.net/skara/pull/1078/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1078&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-323
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1078.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1078/head:pull/1078

PR: https://git.openjdk.java.net/skara/pull/1078