used to change the default for when the option is not
specified.
+--ignore-submodules[=<when>]::
+ Ignore changes to submodules when looking for changes. <when> can be
+ either "none", "untracked", "dirty" or "all", which is the default.
+ Using "none" will consider the submodule modified when it either contains
+ untracked or modified files or its HEAD differs from the commit recorded
+ in the superproject and can be used to override any settings of the
+ 'ignore' option in linkgit:git-config[1] or linkgit:gitmodules[5]. When
+ "untracked" is used submodules are not considered dirty when they only
+ contain untracked content (but they are still scanned for modified
+ content). Using "dirty" ignores all changes to the work tree of submodules,
+ only changes to the commits stored in the superproject are shown (this was
+ the behavior before 1.7.0). Using "all" hides all changes to submodules
+ (and suppresses the output of submodule summaries when the config option
+ `status.submodulesummary` is set).
+
-z::
Terminate entries with NUL, instead of LF. This implies
the `--porcelain` output format if no other format is given.