Add completion on namespace and kubeconfig

This would complete properly the namespaces when we have a -n or files whe we
have kubeconfig

(cherry picked from commit 24839e1)

pkg/cmd/completion/bash_completion.go

@@ -14,6 +14,15 @@
 
 package completion
 
+var (
+	// BashCompletionFlags this maps between a flag (ie: namespace) to a custom
+	// zsh completion
+	BashCompletionFlags = map[string]string{
+		"namespace":  "__kubectl_get_object namespace",
+		"kubeconfig": "_filedir",
+	}
+)
+
 const (
 	// BashCompletionFunc the custom bash completion function to complete object.
 	// The bash completion mechanism will launch the __custom_func func if it cannot
@@ -31,6 +40,17 @@ __tkn_get_object()
 	fi
 }
 
+__kubectl_get_object()
+{
+    local type=$1
+    local template
+    template="{{ range .items  }}{{ .metadata.name }} {{ end }}"
+    local kubectl_out
+    if kubectl_out=$(kubectl get -o template --template="${template}" ${type} 2>/dev/null); then
+        COMPREPLY=( $( compgen -W "${kubectl_out}" -- "$cur" ) )
+    fi
+}
+
 __custom_func() {
 	case ${last_command} in
 		*_describe|*_logs)

pkg/flags/flags.go

@@ -17,6 +17,7 @@ package flags
 import (
 	"github.com/spf13/cobra"
 	"github.com/tektoncd/cli/pkg/cli"
+	"github.com/tektoncd/cli/pkg/cmd/completion"
 )
 
 const (
@@ -33,6 +34,21 @@ func AddTektonOptions(cmd *cobra.Command) {
 	cmd.PersistentFlags().StringP(
 		namespace, "n", "",
 		"namespace to use (default: from $KUBECONFIG)")
+
+	// Add custom completion for that command as specified in
+	// bashCompletionFlags map
+	for name, completion := range completion.BashCompletionFlags {
+		pflag := cmd.PersistentFlags().Lookup(name)
+		if pflag != nil {
+			if pflag.Annotations == nil {
+				pflag.Annotations = map[string][]string{}
+			}
+			pflag.Annotations[cobra.BashCompCustom] = append(
+				pflag.Annotations[cobra.BashCompCustom],
+				completion,
+			)
+		}
+	}
 }
 
 // InitParams initialises cli.Params based on flags defined in command