Options to control how git_status_foreach_ext() will issue callbacks.
This structure is set so that zeroing it out will give you relatively sane defaults.
The show value is one of the git_status_show_t constants that
control which files to scan and in what order.
The flags value is an OR'ed combination of the git_status_opt_t
values above.
The pathspec is an array of path patterns to match (using
fnmatch-style matching), or just an array of paths to match exactly if
GIT_STATUS_OPT_DISABLE_PATHSPEC_MATCH is specified in the flags.
The baseline is the tree to be used for comparison to the working directory
and index; defaults to HEAD.