given again, all changes in $GIT_DIR/index are pushed back to
the shared index file. This mode is designed for very large
indexes that take a significant amount of time to read or write.
++
+These options take effect whatever the value of the `core.splitIndex`
+configuration variable (see linkgit:git-config[1]). But a warning is
+emitted when the change goes against the configured value, as the
+configured value will take effect next time the index is read and this
+will remove the intended effect of the option.
--untracked-cache::
--no-untracked-cache::