Add autocompletion for option values

Closes #555

cmd/micro/autocomplete.go

@@ -148,6 +148,55 @@ func OptionComplete(input string) (string, []string) {
 	return chosen, suggestions
 }
 
+func OptionValueComplete(inputOpt, input string) (string, []string) {
+	inputOpt = strings.TrimSpace(inputOpt)
+	var suggestions []string
+	localSettings := DefaultLocalSettings()
+	var optionVal interface{}
+	for k, option := range globalSettings {
+		if k == inputOpt {
+			optionVal = option
+		}
+	}
+	for k, option := range localSettings {
+		if k == inputOpt {
+			optionVal = option
+		}
+	}
+
+	switch optionVal.(type) {
+	case bool:
+		if strings.HasPrefix("on", input) {
+			suggestions = append(suggestions, "on")
+		} else if strings.HasPrefix("true", input) {
+			suggestions = append(suggestions, "true")
+		}
+		if strings.HasPrefix("off", input) {
+			suggestions = append(suggestions, "off")
+		} else if strings.HasPrefix("false", input) {
+			suggestions = append(suggestions, "false")
+		}
+	case string:
+		switch inputOpt {
+		case "colorscheme":
+			_, suggestions = ColorschemeComplete(input)
+		case "fileformat":
+			if strings.HasPrefix("unix", input) {
+				suggestions = append(suggestions, "unix")
+			}
+			if strings.HasPrefix("dos", input) {
+				suggestions = append(suggestions, "dos")
+			}
+		}
+	}
+
+	var chosen string
+	if len(suggestions) == 1 {
+		chosen = suggestions[0]
+	}
+	return chosen, suggestions
+}
+
 // MakeCompletion registers a function from a plugin for autocomplete commands
 func MakeCompletion(function string) Completion {
 	pluginCompletions = append(pluginCompletions, LuaFunctionComplete(function))

cmd/micro/command.go

@@ -90,7 +90,7 @@ func MakeCommand(name, function string, completions ...Completion) {
 // DefaultCommands returns a map containing micro's default commands
 func DefaultCommands() map[string]StrCommand {
 	return map[string]StrCommand{
-		"set":        {"Set", []Completion{OptionCompletion, NoCompletion}},
+		"set":        {"Set", []Completion{OptionCompletion, OptionValueCompletion}},
 		"setlocal":   {"SetLocal", []Completion{OptionCompletion, NoCompletion}},
 		"show":       {"Show", []Completion{OptionCompletion, NoCompletion}},
 		"bind":       {"Bind", []Completion{NoCompletion}},

cmd/micro/messenger.go

@@ -231,6 +231,7 @@ const (
 	OptionCompletion
 	PluginCmdCompletion
 	PluginNameCompletion
+	OptionValueCompletion
 )
 
 // Prompt sends the user a message and waits for a response to be typed in
@@ -296,6 +297,10 @@ func (m *Messenger) Prompt(prompt, placeholder, historyType string, completionTy
 					chosen, suggestions = HelpComplete(currentArg)
 				} else if completionType == OptionCompletion {
 					chosen, suggestions = OptionComplete(currentArg)
+				} else if completionType == OptionValueCompletion {
+					if currentArgNum-1 > 0 {
+						chosen, suggestions = OptionValueComplete(args[currentArgNum-1], currentArg)
+					}
 				} else if completionType == PluginCmdCompletion {
 					chosen, suggestions = PluginCmdComplete(currentArg)
 				} else if completionType == PluginNameCompletion {