Only one of ValidArgs/ValidArgsFunction at a time

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

bash_completions.md

@@ -117,7 +117,8 @@ In some cases it is not possible to provide a list of possible completions in ad
 
 #### 1. Custom completions of nouns written in Go
 
-In a similar fashion as for static completions, you can use the `validArgsFunction` field to provide a Go function that Cobra will execute when it needs the list of completion choices for the nouns of a command.  Simplified code from `helm status` looks like:
+In a similar fashion as for static completions, you can use the `ValidArgsFunction` field to provide a Go function that Cobra will execute when it needs the list of completion choices for the nouns of a command.  Note that either `ValidArgs` or `ValidArgsFunction` can be used for a single cobra command, but not both.
+Simplified code from `helm status` looks like:
 
 ```go
 cmd := &cobra.Command{

command.go

@@ -59,6 +59,7 @@ type Command struct {
 	ValidArgs []string
 	// ValidArgsFunction is an optional function that provides valid non-flag arguments for bash completion.
 	// It is a dynamic version of using ValidArgs.
+	// Only one of ValidArgs and ValidArgsFunction can be used for a command.
 	ValidArgsFunction func(cmd *Command, args []string, toComplete string) ([]string, BashCompDirective)
 
 	// Expected arguments