--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/mercurial.lua	Wed Jan 21 02:55:18 2015 +0100
@@ -0,0 +1,34 @@
+
+local lfs = require"lfs";
+
+local hg = { };
+
+function hg.check_id(path)
+	if lfs.attributes(path, 'mode') ~= "directory" then
+		return nil, "not a directory";
+	end
+	local hg_dirstate = io.open(path.."/.hg/dirstate");
+	local hgid, hgrepo
+	if hg_dirstate then
+		hgid = ("%02x%02x%02x%02x%02x%02x"):format(hg_dirstate:read(6):byte(1, 6));
+		hg_dirstate:close();
+		local hg_changelog = io.open(path.."/.hg/store/00changelog.i");
+		if hg_changelog then
+			hg_changelog:seek("set", 0x20);
+			hgrepo = ("%02x%02x%02x%02x%02x%02x"):format(hg_changelog:read(6):byte(1, 6));
+			hg_changelog:close();
+		end
+	else
+		local hg_archival,e = io.open(path.."/.hg_archival.txt");
+		if hg_archival then
+			local repo = hg_archival:read("*l");
+			local node = hg_archival:read("*l");
+			hg_archival:close()
+			hgid = node and node:match("^node: (%x%x%x%x%x%x%x%x%x%x%x%x)")
+			hgrepo = repo and repo:match("^repo: (%x%x%x%x%x%x%x%x%x%x%x%x)")
+		end
+	end
+	return hgid, hgrepo;
+end
+
+return hg;