-R flag for grep not universally supported

[Jamie Jennings]

Attempting to use dot-only-hunter on Alpine Linux results in a grep error:

$ dot-only-hunter
Hunting inside 'test' for tests with `.only`...
grep: unrecognized option: R
BusyBox v1.24.2 (2016-08-12 14:38:34 GMT) multi-call binary.

Usage: grep [-HhnlLoqvsriwFE] [-m N] [-A/B/C N] PATTERN/-e PATTERN.../-f FILE [FILE]...

Search for PATTERN in FILEs (or stdin)

	-H	Add 'filename:' prefix
	-h	Do not add 'filename:' prefix
	-n	Add 'line_no:' prefix
	-l	Show only names of files that match
	-L	Show only names of files that don't match
	-c	Show only count of matching lines
	-o	Show only the matching part of line
	-q	Quiet. Return 0 if PATTERN is found, 1 otherwise
	-v	Select non-matching lines
	-s	Suppress open and read errors
	-r	Recurse
	-i	Ignore case
	-w	Match whole words only
	-x	Match whole lines only
	-F	PATTERN is a literal (not regexp)
	-E	PATTERN is an extended regexp
	-m N	Match up to N times per file
	-A N	Print N lines of trailing context
	-B N	Print N lines of leading context
	-C N	Same as '-A N -B N'
	-e PTRN	Pattern to match
	-f FILE	Read pattern from file
All good!

Furthermore, due to #1, dot-only-hunter reports success in this case.

[David da Silva]

To solve this one, I'd rather make dot-only-hunter detect support for -R and fallback from -R to -r if necessary.

Adding the pr-welcome label.