v1 was here:
https://www.redhat.com/archives/libguestfs/2018-November/msg00147.html
v2:
- Use stdbool for booleans.
- Use __attribute__((format(printf))).
- Don't abort on invalid options, exit with failure instead.
- Preserve long/short option choices in the output.
- Add '=' in long option output, ie. always use --longopt=arg.
- Add "--" parameter (unconditionally) before non-options.
- Fix comments that referred to "alphanumeric" plugin and filter names.
- Retested.
Rich.