Implement *Context.GlobalSet + relevant CHANGELOG entry

context.go

@@ -146,6 +146,11 @@ func (c *Context) Set(name, value string) error {
 	return c.flagSet.Set(name, value)
 }
 
+// GlobalSet sets a context flag to a value on the global flagset
+func (c *Context) GlobalSet(name, value string) error {
+	return globalContext(c).flagSet.Set(name, value)
+}
+
 // Determines if the flag was actually set
 func (c *Context) IsSet(name string) bool {
 	if c.setFlags == nil {
@@ -252,6 +257,21 @@ func (a Args) Swap(from, to int) error {
 	return nil
 }
 
+func globalContext(ctx *Context) *Context {
+	if ctx == nil {
+		return nil
+	}
+
+	for {
+		if ctx.parentContext == nil {
+			return ctx
+		}
+		ctx = ctx.parentContext
+	}
+
+	return nil
+}
+
 func lookupGlobalFlagSet(name string, ctx *Context) *flag.FlagSet {
 	if ctx.parentContext != nil {
 		ctx = ctx.parentContext