simplify example in helptext. add testdata.

borg/archiver.py

@@ -1013,8 +1013,6 @@ class Archiver:
             # susan is a nice person
             # include susans home
             + /home/susan
-            # ... and its contents
-            + /home/susan/*
             # don't backup the other home directories
             - /home/*
 

borg/testsuite/helpers.py

@@ -508,6 +508,9 @@ def test_load_invalid_patterns_from_file(tmpdir, lines):
     (["+fm:*/something00.txt",
       "-/data"],
      ["/data/something00.txt", '/home', '/home/leo', '/home/leo/t', '/home/other']),
+    (["+/home/leo",
+      "-/home/*"],
+     ['/data', '/data/something00.txt', '/data/subdir/something01.txt', '/home', '/home/leo', '/home/leo/t']),
     (["+fm:/home/leo",
       "-/home/"],
      ['/data', '/data/something00.txt', '/data/subdir/something01.txt', '/home', '/home/leo', '/home/leo/t']),