Mention custom args in help text.

Author: maleadt

src/ParallelTestRunner.jl

@@ -505,18 +505,24 @@ function parse_args(args; custom::Array{String} = String[])
 
     help = extract_flag!(args, "--help")
     if help !== nothing
-        println(
+        usage =
             """
             Usage: runtests.jl [--help] [--list] [--jobs=N] [TESTS...]
 
                --help             Show this text.
                --list             List all available tests.
                --verbose          Print more information during testing.
                --quickfail        Fail the entire run as soon as a single test errored.
-               --jobs=N           Launch `N` processes to perform tests.
+               --jobs=N           Launch `N` processes to perform tests."""
 
-               Remaining arguments filter the tests that will be executed."""
-        )
+        if !isempty(custom)
+            usage *= "\n\nCustom arguments:"
+            for flag in custom
+                usage *= "\n   --$flag"
+            end
+        end
+        usage *= "\n\nRemaining arguments filter the tests that will be executed."
+        println(usage)
         exit(0)
     end