fs: re-implement CutoffMode, LogLevel, TerminalColorMode with Enum

This almost 100% backwards compatible. The only difference being that
in the rc options/get output CutoffMode, LogLevel, TerminalColorMode
will be output as strings instead of integers. This is a lot more
convenient for the user. They still accept integer inputs though so
the fallout from this should be minimal.

fs/cutoffmode.go

@@ -1,58 +1,22 @@
 package fs
 
-import (
-	"fmt"
-	"strings"
-)
+type cutoffModeChoices struct{}
+
+func (cutoffModeChoices) Choices() []string {
+	return []string{
+		CutoffModeHard:     "HARD",
+		CutoffModeSoft:     "SOFT",
+		CutoffModeCautious: "CAUTIOUS",
+	}
+}
 
 // CutoffMode describes the possible delete modes in the config
-type CutoffMode byte
+type CutoffMode = Enum[cutoffModeChoices]
 
-// MaxTransferMode constants
+// CutoffMode constants
 const (
 	CutoffModeHard CutoffMode = iota
 	CutoffModeSoft
 	CutoffModeCautious
 	CutoffModeDefault = CutoffModeHard
 )
-
-var cutoffModeToString = []string{
-	CutoffModeHard:     "HARD",
-	CutoffModeSoft:     "SOFT",
-	CutoffModeCautious: "CAUTIOUS",
-}
-
-// String turns a LogLevel into a string
-func (m CutoffMode) String() string {
-	if m >= CutoffMode(len(cutoffModeToString)) {
-		return fmt.Sprintf("CutoffMode(%d)", m)
-	}
-	return cutoffModeToString[m]
-}
-
-// Set a LogLevel
-func (m *CutoffMode) Set(s string) error {
-	for n, name := range cutoffModeToString {
-		if s != "" && name == strings.ToUpper(s) {
-			*m = CutoffMode(n)
-			return nil
-		}
-	}
-	return fmt.Errorf("unknown cutoff mode %q", s)
-}
-
-// Type of the value
-func (m CutoffMode) Type() string {
-	return "string"
-}
-
-// UnmarshalJSON makes sure the value can be parsed as a string or integer in JSON
-func (m *CutoffMode) UnmarshalJSON(in []byte) error {
-	return UnmarshalJSONFlag(in, m, func(i int64) error {
-		if i < 0 || i >= int64(len(cutoffModeToString)) {
-			return fmt.Errorf("out of range cutoff mode %d", i)
-		}
-		*m = (CutoffMode)(i)
-		return nil
-	})
-}