[[licenses.clarify]]: license-files can't contain files that don't start with LICENSE

[str4d]

I am trying to add two license files to a [[licenses.clarify]]: one named LICENSE-FOO (describing the base license), and one named COPYING (describing how the base license applies to the project). The former file can be found and pinned, but the latter cannot.

The problem is that the license-files in each clarification are not directly searched for, but instead checked against the list of discovered license files, obtained from LicensePack::read, which filters out any file that doesn't start with LICENSE:

cargo-deny/src/licenses/gather.rs

Lines 533 to 556 in 9ca5722

	for clarification in iter_clarifications(&cfg.clarifications, krate) {
	let lp = if let Some(lp) = &license_pack {
	lp
	} else {
	license_pack = Some(LicensePack::read(krate));
	license_pack.as_ref().unwrap()
	};
	// Check to see if the clarification provided exactly matches
	// the set of detected licenses, if they do, we use the clarification's
	// license expression as the license requirements for this crate
	let clarifications_match = clarification.license_files.iter().all(|clf| {
	match lp.license_files_match(clf) {
	Ok(_) => true,
	Err(reason) => {
	if let MismatchReason::FileNotFound = reason {
	labels.push(
	super::diags::MissingClarificationFile {
	expected: &clf.path,
	cfg_file_id: cfg.file_id,
	}
	.into(),
	);
	}

cargo-deny/src/licenses/gather.rs

Lines 139 to 143 in 9ca5722

	impl LicensePack {
	fn read(krate: &Krate) -> Self {
	let root_path = krate.manifest_path.parent().unwrap();
	let mut lic_paths = match find_license_files(root_path) {

cargo-deny/src/licenses/gather.rs

Lines 50 to 54 in 9ca5722

	if p.is_file() && p.file_name().map_or(false, |f| f.starts_with("LICENSE")) {
	Some(p)
	} else {
	None
	}

[str4d]

If the filtering is intentional (i.e. cargo-deny has an allow-list of filenames that can be considered to contain licenses), then it would be good to both add COPYING as an allowed filename (or filename prefix, though IDK how common the latter is), and return an error message that tells the user about the filter mismatch (rather than the more obtuse "file not found").