
========================================
plan -1:
* "grep regexp ." should fail with ". Is a directory"
* --exclude-dir

========================================
plan 0:
* multiple -m<N> -- use the latest one, same for -C, -A, -B etc.
* --include-from=FILE
* --exclude-dir=PATTERN  directories that match PATTERN will be skipped.
* JGREP_COLORS
* additional option for counting all found instances instead of matched lines

========================================
plan 0.5:
* get rid of Apache Commons libraries. Use plain JDK-8

========================================
plan 1:
* -v + -C + coloring
* reusable object Jgrep. I/O streams etc.
* -O with named capturing groups?

========================================
The following GNU grep options are not implemented and probably won't be:
* -E, --extended-regexp     PATTERN is an extended regular expression (ERE)
* -G, --basic-regexp        PATTERN is a basic regular expression (BRE)
* -P, --perl-regexp         PATTERN is a Perl regular expression
* -b, --byte-offset         print the byte offset with output lines
*     --binary-files=TYPE   assume that binary files are TYPE;
*                           TYPE is 'binary', 'text', or 'without-match'
* -a, --text                equivalent to --binary-files=text
* -I                        equivalent to --binary-files=without-match
* -D, --devices=ACTION      how to handle devices, FIFOs and sockets;
                            ACTION is 'read' or 'skip'
* -NUM                      same as --context=NUM

========================================
Won't be supported? 
* -z, --null-data           a data line ends in 0 byte, not newline
* -T, --initial-tab         make tabs line up (if needed)
* -Z, --null                print 0 byte after FILE name
* -b option
* -u option
* -a,--text option
* --binary-files
* -D ACTION, --devices=ACTION
* -I
* -U, --binary              do not strip CR characters at EOL (MSDOS/Windows)
* -u, --unix-byte-offsets   report offsets as if CRs were not there
                            (MSDOS/Windows)
