Define and register 'detect' subcommand

plugins/buildpacks/Makefile

@@ -1,4 +1,4 @@
-SUBCOMMANDS = subcommands/add subcommands/clear subcommands/list subcommands/remove subcommands/report subcommands/set subcommands/set-property
+SUBCOMMANDS = subcommands/add subcommands/clear subcommands/detect subcommands/list subcommands/remove subcommands/report subcommands/set subcommands/set-property
 TRIGGERS = triggers/buildpack-stack-name triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-delete triggers/post-extract triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = buildpacks

plugins/buildpacks/src/subcommands/subcommands.go

@@ -30,6 +30,11 @@ func main() {
 		args.Parse(os.Args[2:])
 		appName := args.Arg(0)
 		err = buildpacks.CommandClear(appName)
+	case "detect":
+		args := flag.NewFlagSet("buildpacks:detect", flag.ExitOnError)
+		args.Parse(os.Args[2:])
+		appName := args.Arg(0)
+		err = buildpacks.CommandDetect(appName)
 	case "list":
 		args := flag.NewFlagSet("buildpacks:list", flag.ExitOnError)
 		args.Parse(os.Args[2:])

plugins/buildpacks/subcommands.go

@@ -3,6 +3,7 @@ package buildpacks
 import (
 	"errors"
 	"fmt"
+	"os"
 
 	"github.com/dokku/dokku/plugins/common"
 )
@@ -30,6 +31,51 @@ func CommandClear(appName string) error {
 	return common.PropertyDelete("buildpacks", appName, "buildpacks")
 }
 
+// CommandDetect implements buildpacks:detect
+func CommandDetect(appName string) error {
+	if err := common.VerifyAppName(appName); err != nil {
+		return err
+	}
+
+	buildPath := common.AppRoot(appName)
+	if !common.DirectoryExists(buildPath) {
+		return fmt.Errorf("App %s does not exist", appName)
+	}
+
+	workDir := buildPath
+	if isBareGitRepo(buildPath) {
+		checkedOutPath, err := checkoutBareGitRepo(buildPath)
+        if err != nil {
+            return err
+        }
+		workDir = checkedOutPath
+		defer func() {
+			if err := os.RemoveAll(checkedOutPath); err != nil {
+				common.LogWarn(fmt.Sprintf("Failed to remove temporary directory %s: %v", checkedOutPath, err))
+			}
+		}()
+	}
+
+	appRoot := workDir
+
+	dockerArgs := []string{
+		"run", "--rm",
+		"-v", fmt.Sprintf("%s:/tmp/app", appRoot),
+		"gliderlabs/herokuish", "/bin/herokuish", "buildpack", "detect", "/tmp/app",
+	}
+
+	result, err := common.CallExecCommand(common.ExecCommandInput{
+		Command: common.DockerBin(),
+		Args:    dockerArgs,
+	})
+	if err != nil {
+		return fmt.Errorf("Buildpack detection failed: %s", result.StderrContents())
+	}
+
+	common.LogVerbose(fmt.Sprintf("%s", result.StdoutContents()))
+	return nil
+}
+
 // CommandList implements buildpacks:list
 func CommandList(appName string) (err error) {
 	if err := common.VerifyAppName(appName); err != nil {