fixed incorrect backslashes escaping outside of tokens

src/base/detoken.lua

@@ -110,7 +110,7 @@
 			local count
 			repeat
 				value, count = value:gsub("%%{(.-)}", function(token)
-					local result, err = expandtoken(token, environ)
+					local result, err = expandtoken(token:gsub("\\", "\\\\"), environ)
 					if not result then
 						error(err, 0)
 					end
@@ -139,8 +139,7 @@
 				end
 				return value
 			else
-				-- escape backslashes: they will break loadstring
-				return expandvalue(value:gsub("\\", "\\\\"))
+				return expandvalue(value)
 			end
 		end
 

tests/base/test_detoken.lua

@@ -129,3 +129,13 @@
 		x = detoken.expand("%{foo:gsub('/', '\\')}", environ)
 		test.isequal("some\\path", x)
 	end
+
+--
+-- Escapes backslashes correctly, but not outside tokens.
+--
+
+	function suite.escapesBackslashes2()
+		environ.foo = "some/path"
+		x = detoken.expand("%{foo:gsub('/', '\\')}\\already\\escaped", environ)
+		test.isequal("some\\path\\already\\escaped", x)
+	end