*flags* may be RENAME_EXCHANGE or RENAME_NOREPLACE.
If RENAME_NOREPLACE is specified, the filesystem must not
overwrite *dst* if it exists and throw an error instead.
If RENAME_EXCHANGE is specified, the filesystem must atomically
exchange the two files, i.e. both must exist and neither may be deleted.
Rename a file.
*flags* may be RENAME_EXCHANGE or RENAME_NOREPLACE. If RENAME_NOREPLACE is specified, the filesystem must not overwrite *dst* if it exists and throw an error instead. If RENAME_EXCHANGE is specified, the filesystem must atomically exchange the two files, i.e. both must exist and neither may be deleted.