Add support for Kubectl plugins.

Author: brendandburns

README.md

@@ -131,6 +131,22 @@ Try out an example
 
 Read the [docs](https://github.com/brendandburns/configula/tree/master/docs)
 
+### Integrating with Kubernetes
+Configula can be used as a `kubectl` plugin.
+
+To install the plugin run this command:
+
+```
+# assumes that configula is in /usr/local/bin/ change paths as needed.
+ln -s /usr/local/bin/kubectl-configula /usr/local/bin/configula
+```
+
+Once that's done you can run:
+
+```sh
+kubectl configula create -f examples/namespaces.py
+```
+
 ### FAQ
 *What about other Javascript? Java? Go? .NET? Other Language?*
 

cmd/configula/main.go

@@ -2,6 +2,9 @@ package main
 
 import (
 	"fmt"
+	"os/exec"
+	"io"
+	"strings"
 	"os"
 
 	"github.com/brendandburns/configula/pkg/configula"
@@ -11,15 +14,43 @@ import (
 var (
 	pythonCommand = flag.String("python", "python3", "The executable to run for Python, overridden by $CONFIGULA_PYTHON")
 	dryRun        = flag.Bool("debug", false, "If true, only output the interim program, don't execute")
+	file = flag.StringP("filename", "f", "", "The file name to process")
 )
 
+func pluginMain() {
+	if len(*file) == 0 || len(flag.Args()) != 1 {
+		fmt.Fprintf(os.Stderr, "Usage: kubectl configula create|apply|delete -f <some-file>\n")
+		return
+	}
+	cmd := exec.Command("kubectl", flag.Args()[0], "-f", "-")
+	output, err := cmd.StdinPipe()
+	if err != nil {
+		panic(err)
+	}
+	go func() {
+		process(*file, output)
+		if err := output.Close(); err != nil {
+			panic(err)
+		}
+	}()
+	cmd.Run()
+}
+
 func main() {
 	flag.Parse()
+	if strings.HasSuffix(os.Args[0], "kubectl-configula") {
+		pluginMain()
+		return
+	}
 	if len(flag.Args()) == 0 {
 		fmt.Fprintf(os.Stderr, "Usage: configula [--debug] [--python=/some/path] <path/to/config/file>\n")
 		os.Exit(-1)
 	}
-	file, err := os.Open(flag.Args()[0])
+	process(flag.Args()[0], os.Stdout)
+}
+
+func process(filename string, output io.Writer) {
+	file, err := os.Open(filename)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to read %s: %s", flag.Args()[0], err.Error())
 		os.Exit(1)
@@ -38,7 +69,7 @@ func main() {
 		configula.NewPythonExecutor(pythonExec),
 	}
 
-	if err := rn.Run(file, os.Stdout, *dryRun); err != nil {
+	if err := rn.Run(file, output, *dryRun); err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to execute: %s", err)
 		os.Exit(-1)
 	}