command: root early handler func special case

This allows for early initialisation with access to flags on the root node. This can be useful for configuring global state used by subcommands.

Signed-off-by: Ophestra <cat@gensokyo.uk>

command/builder.go

@@ -7,8 +7,10 @@ import (
 )
 
 // New initialises a root Node.
-func New(output io.Writer, logf LogFunc, name string) Command {
-	return rootNode{newNode(output, logf, name, "")}
+func New(output io.Writer, logf LogFunc, name string, early HandlerFunc) Command {
+	c := rootNode{newNode(output, logf, name, "")}
+	c.f = early
+	return c
 }
 
 func newNode(output io.Writer, logf LogFunc, name, usage string) *node {