Update command_line.rst: reflect current --help info

Author: wyattscarpenter

docs/source/command_line.rst

@@ -1255,12 +1255,18 @@ Miscellaneous
    stub packages were found, they are installed and then another run
    is performed.
 
-.. option:: --junit-xml JUNIT_XML
+.. option:: --junit-xml JUNIT_XML_OUTPUT_FILE
 
     Causes mypy to generate a JUnit XML test result document with
     type checking results. This can make it easier to integrate mypy
     with continuous integration (CI) tools.
 
+.. option:: --junit-format {global,per_file}
+
+    If --junit-xml is set, specifies format.
+    global (default): single test with all errors;
+    per_file: one test entry per file with failures.
+
 .. option:: --find-occurrences CLASS.MEMBER
 
     This flag will make mypy print out all usages of a class member