Document stdin behaviour for getting raw key

Document the logic described in makeRawKey.

diff --git a/cmd/fscrypt/flags.go b/cmd/fscrypt/flags.go
index 7285133000e76d9c3603a657ee4de6d783e2bf12..3d3c51d50ba9bfa1a6e4aa3a2ab128774c1f8b3a 100644 (file)
--- a/cmd/fscrypt/flags.go
+++ b/cmd/fscrypt/flags.go
@@ -222,7 +222,8 @@ var (
                Usage: `Use the contents of FILE as the wrapping key when
                        creating or unlocking raw_key protectors. FILE should be
                        formatted as raw binary and should be exactly 32 bytes
-                       long.`,
+                       long. When running non-interactively and no key is provided,
+                       will try to read the key from stdin.`,
        }
        userFlag = &stringFlag{
                Name:    "user",