Status flags for a single file.
A combination of these values will be returned to indicate the status of
a file. Status compares the working directory, the index, and the
current HEAD of the repository. The GIT_STATUS_INDEX
set of flags
represents the status of file in the index relative to the HEAD, and the
GIT_STATUS_WT
set of flags represent the status of the file in the
working directory relative to the index.