build: Allow alphanumeric test name suffixes

To allow test names to be more descriptive, allow a suffix to be
added to the numeric name of the test.  e.g. a test can be named
"tests/generic/001-some-descriptive-name".

Name suffixes are limited to alphanumeric characters and dash - the
name is always prefixed with an unique id for easy identification
of a specific test. Hence we can still use shorthand forms such as
"generic/001" when referring to a test and be clearly understood.

Signed-off-by: Jan Tulak <jtulak@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

README

@@ -202,10 +202,16 @@ Test script environment:
 	- When calling getfacl in a test, pass the "-n" argument so
 	  that numeric rather than symbolic identifiers are used in
 	  the output.
+	- When creating a new test, it is possible to enter a custom name
+	  for the file. Filenames are in form NNN-custom-name, where NNN
+	  is automatically added by the ./new script as an unique ID,
+	  and "custom-name" is the optional string entered into a prompt
+	  in the ./new script. It can contain only alphanumeric characters
+	  and dash. Note the "NNN-" part is added automatically.
 
 Verified output:
 
-    Each test script has a numerical name, e.g. 007, and an associated
+    Each test script has a name, e.g. 007, and an associated
     verified output, e.g. 007.out.
 
     It is important that the verified output is deterministic, and