Add additional documentation

Signed-off-by: Sascha Grunert <mail@saschagrunert.de>

suggestions.go

@@ -31,6 +31,8 @@ func (a *App) suggestFlagFromError(err error, command string) (string, error) {
 	return fmt.Sprintf(didYouMeanTemplate+"\n\n", suggestion), nil
 }
 
+// suggestFlag takes a list of flags and a provided string to suggest a
+// flag name by calculating the Jaro Winkler distance.
 func (a *App) suggestFlag(flags []Flag, provided string) (suggestion string) {
 	distance := 0.0
 
@@ -40,6 +42,9 @@ func (a *App) suggestFlag(flags []Flag, provided string) (suggestion string) {
 			flagNames = append(flagNames, HelpFlag.Names()...)
 		}
 		for _, name := range flagNames {
+			// JaroWinkler computes the Jaro-Winkler edit distance between two
+			// strings. This is a modification of the Jaro algorithm that gives
+			// additional weight to prefix matches.
 			newDistance := matchr.JaroWinkler(name, provided, true)
 			if newDistance > distance {
 				distance = newDistance
@@ -58,11 +63,14 @@ func (a *App) suggestFlag(flags []Flag, provided string) (suggestion string) {
 }
 
 // suggestCommand takes a list of commands and a provided string to suggest a
-// command name
+// command name by calculating the Jaro Winkler distance.
 func suggestCommand(commands []*Command, provided string) (suggestion string) {
 	distance := 0.0
 	for _, command := range commands {
 		for _, name := range append(command.Names(), helpName, helpAlias) {
+			// JaroWinkler computes the Jaro-Winkler edit distance between two
+			// strings. This is a modification of the Jaro algorithm that gives
+			// additional weight to prefix matches.
 			newDistance := matchr.JaroWinkler(name, provided, true)
 			if newDistance > distance {
 				distance = newDistance