Make it so readHumdrum() can be fed a url.

[SileYin]

There is a base-R url() function. It would be nice if readHumdrum could somehow read either a single file or a collection of files directly from a url.

For example, there is a single file here: https://raw.githubusercontent.com/josquin-research-project/Jos/main/Jos0703b-Missa_Dung_aultre_amer-Gloria.krn

[SileYin]

Now supports read single file from url string in branch read_from_url.

I can successfully load a humdrum file such as:

readHumdrum('https://raw.githubusercontent.com/Computational-Cognitive-Musicology-Lab/humdrumR/main/inst/HumdrumData/BachChorales/chor001.krn')

However, I don't know whether it is because of this specific file or something else, reading this file gives me error:

readHumdrum('https://raw.githubusercontent.com/josquin-research-project/Jos/main/Jos0703b-Missa_Dung_aultre_amer-Gloria.krn')

Finding and reading files...
	REpath-pattern 'https://raw.githubusercontent.com/josquin-research-project/Jos/main/Jos0703b-Missa_Dung_aultre_amer-Gloria.krn' matches 1 text files in 1 directory.
One files read from disk.
Validating one files...all valid.
Parsing one files...
Error in mat[, 1] : subscript out of bounds
9.
is.factor(x)
8.
grepl("^\\*>", spine) at Read.R#1223
7.
parseSections(mat[, 1]) at Read.R#863
6.
parseLocal(records) at Read.R#740
5.
parseRecords(file, piece, reference) at Read.R#688
4.
(function (file, piece)
{
humtab <- parseRecords(file, piece, reference)
if (verbose) ...
3.
mapply(FUN = f, ..., SIMPLIFY = FALSE)
2.
Map(function(file, piece) {
humtab <- parseRecords(file, piece, reference)
if (verbose)
message(filename, "\n") ... at Read.R#686
1.
readHumdrum("https://raw.githubusercontent.com/josquin-research-project/Jos/main/Jos0703b-Missa_Dung_aultre_amer-Gloria.krn")