Merge branch 'as/check-ignore'

Enhance "check-ignore" (1.8.2 update) to work more like "check-attr" over bidi-pipes. * as/check-ignore: t0008: use named pipe (FIFO) to test check-ignore streaming Documentation: add caveats about I/O buffering for check-{attr,ignore} check-ignore: allow incremental streaming of queries via --stdin check-ignore: move setup into cmd_check_ignore() check-ignore: add -n / --non-matching option t0008: remove duplicated test fixture data