Don't use -o for 'omit' in the new command syntax: it should mean output.

1 files changed, 8 insertions, 2 deletions

diff --git a/coverage/cmdline.py b/coverage/cmdline.py
index 587fac51..8d9c239f 100644
--- a/coverage/cmdline.py
+++ b/coverage/cmdline.py
@@ -31,12 +31,18 @@ class Opts:
         help="Show line numbers of statements in each module that weren't "
                 "executed."
         )
-    omit = optparse.Option(
+    old_omit = optparse.Option(
         '-o', '--omit', action='store',
         metavar="PRE1,PRE2,...",
         help="Omit files when their filename path starts with one of these "
                 "prefixes."
         )
+    omit = optparse.Option(
+        '', '--omit', action='store',
+        metavar="PRE1,PRE2,...",
+        help="Omit files when their filename path starts with one of these "
+                "prefixes."
+        )
     parallel_mode = optparse.Option(
         '-p', '--parallel-mode', action='store_true',
         help="Include the machine name and process id in the .coverage "
@@ -123,7 +129,7 @@ class ClassicOptionParser(CoverageOptionParser):
             Opts.ignore_errors,
             Opts.pylib,
             Opts.show_missing,
-            Opts.omit,
+            Opts.old_omit,
             Opts.parallel_mode,
             Opts.timid,
         ])