cryptocore, main: add two comments

While reading the code, I had to think about what it
does, so add a comment that explains it.

internal/cryptocore/cryptocore.go

@@ -53,6 +53,9 @@ type CryptoCore struct {
 // Even though the "GCMIV128" feature flag is now mandatory, we must still
 // support 96-bit IVs here because they were used for encrypting the master
 // key in gocryptfs.conf up to gocryptfs v1.2. v1.3 switched to 128 bits.
+//
+// Note: "key" is either the scrypt hash of the password (when decrypting
+// a config file) or the masterkey (when finally mounting the filesystem).
 func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDecode bool) *CryptoCore {
 	if len(key) != KeyLen {
 		log.Panic(fmt.Sprintf("Unsupported key length %d", len(key)))

main.go

@@ -67,6 +67,8 @@ func changePassword(args *argContainer) {
 	newPw := readpassword.Twice(args.extpass)
 	readpassword.CheckTrailingGarbage()
 	confFile.EncryptKey(masterkey, newPw, confFile.ScryptObject.LogN())
+	// Are we resetting the password without knowing the old one using
+	// "-masterkey"?
 	if args.masterkey != "" {
 		bak := args.config + ".bak"
 		err = os.Link(args.config, bak)