Expose parsed ref string

[jennybc]

This is going to be handy elsewhere:

Make sure I can get Sheet1 from reasonable representations of Sheet1!$B$2:$B$11.

[jennybc]

Upon further thought, I think I need to make parse_ref_string() nicer and export it:

cellranger/R/A1-R1C1-regex-utils.R

Lines 89 to 105 in 652fa2d

	parse_ref_string <- function(x, fo = NULL) {
	parsed <- as.list(rematch::re_match(.cr$string_rx, x)[1, , drop = TRUE])
	names(parsed) <- c("input", "file", "sheet", "ref", "invalid")
	parsed$ref_v <- unlist(strsplit(parsed$ref, ":"))
	stopifnot(length(parsed$ref_v) %in% 1:2)
	if (is.null(fo)) {
	fo_v <- guess_fo(parsed$ref_v)
	parsed$fo <- unique(fo_v)
	if (length(parsed$fo) > 1) {
	stop("Cell references aren't uniformly A1 or R1C1 format:\n",
	parsed$ref, call. = FALSE)
	}
	} else {
	parsed$fo <- match.arg(fo, c("R1C1", "A1"))
	}
	parsed
	}

Re: the cell ref specifically, parsed output should include ref and probably ul and lr. Examples:

ref = $B$2, ul and lr are either both $B$2 or both NA

ref = $B$2:$B$11, ul = $B$2, lr = $B$11