docs: add common options to documentation

These can be found by running `semantic-release --help`, but including them
in the documentation will be helpful for CI users who don't have the command
installed locally.

Related to #327.

docs/commands.rst

@@ -53,3 +53,44 @@ Publish will do a sequence of things:
 #. Attach the files created by :ref:`config-build_command` to GitHub releases.
 
 Some of these steps may be disabled based on your configuration.
+
+Common Options
+~~~~~~~~~~~~~~
+
+Every command understands these flags:
+
+``--patch``
+...........
+
+Force a patch release, ignoring the version bump determined from commit messages.
+
+``--minor``
+...........
+
+Force a minor release, ignoring the version bump determined from commit messages.
+
+``--major``
+...........
+
+Force a major release, ignoring the version bump determined from commit messages.
+
+``--noop``
+..........
+
+No operations mode. Do not take any actions, only print what will be done.
+
+``--retry``
+...........
+
+Retry the same release, do not bump.
+
+``--define``
+............
+
+Override a configuration value. Takes an argument of the format
+``setting="value"``.
+
+``--verbosity``
+...............
+
+Change the verbosity of Python Semantic Release's logging. See :ref:`debug-usage`.