fix: update cli usage for proto indexer
// default, this program reads a single Proto compilation unit from stdin and
// emits binary Kythe artifacts to stdout as a sequence of Entity protos.
//
-// eg: indexer -i foo.proto -o foo.bin
-// indexer -i foo.proto | verifier foo.proto
+// eg: indexer foo.proto -o foo.bin
+// indexer foo.proto | verifier foo.proto
// indexer -index_file some/file.kzip
+// cat foo.proto | indexer | verifier foo.proto
#include <fcntl.h>
#include <sys/stat.h>
