auto-create magic config.json on magic init

Signed-off-by: Josh Dolitsky <josh@dolit.ski>

README.md

@@ -85,18 +85,19 @@ Creating directory '/Users/me/Library/Application Support/magic/etc' ...
 Creating mapping file '/Users/me/Library/Application Support/magic/etc/aws.yml' ...
 Creating mapping file '/Users/me/Library/Application Support/magic/etc/azure.yml' ...
 Creating mapping file '/Users/me/Library/Application Support/magic/etc/gcp.yml' ...
+Creating magic config file '/Users/me/Library/Application Support/magic/config.json' ...
 ```
 
-If you wish to make `magic` the default credential helper, manually modify
-the `credsStore` field in `$HOME/.docker/config.json`:
+Next, modify the `DOCKER_CONFIG` env var to point to the magic directory:
 
-```javascript
-{
-  // ...
-  "credsStore": "magic",
-  // ...
-}
 ```
+$ export DOCKER_CONFIG="$(docker-credential-magic home)"
+```
+
+You may wish to add the previous command to your `~/.bashrc` / `~/.bash_profile`.
+
+If no matching domains are found, `magic` will fall back to use
+your existing `$HOME/.docker/config.json`.
 
 Note: At this time, `magic` will not automatically install the supported
 helpers on your machine. You should install each of these manually.

cmd/docker-credential-magic/main.go

@@ -45,8 +45,8 @@ func main() {
 	switch subcommand {
 	case constants.HelperSubcommandGet:
 		subcommandGet()
-	case "env":
-		subcommandEnv()
+	case "home":
+		subcommandHome()
 	case "init":
 		subcommandInit()
 	case "version":
@@ -56,7 +56,7 @@ func main() {
 }
 
 func usage() {
-	fmt.Printf("Usage: docker-credential-magic <%s|env|init|version>\n",
+	fmt.Printf("Usage: docker-credential-magic <%s|home|init|version>\n",
 		constants.HelperSubcommandGet)
 	os.Exit(1)
 }
@@ -137,27 +137,25 @@ func subcommandGet() {
 	os.Exit(0)
 }
 
-func subcommandEnv() {
+func subcommandHome() {
 	dockerCredentialMagicConfig := getDockerCredentialMagicConfig()
-	fmt.Printf("%s=\"%s\"\n",
-		constants.EnvVarDockerCredentialMagicConfig,
-		dockerCredentialMagicConfig)
+	fmt.Println(dockerCredentialMagicConfig)
 	os.Exit(0)
 }
 
 func subcommandInit() {
 	dockerCredentialMagicConfig := getDockerCredentialMagicConfig()
-	parentDir := filepath.Join(dockerCredentialMagicConfig, constants.MappingsSubdir)
-	parentDirAbs, err := filepath.Abs(parentDir)
+	dockerCredentialMagicConfigDirAbs, err := filepath.Abs(dockerCredentialMagicConfig)
 	if err != nil {
 		fmt.Printf("Error: '%s' is not a valid directory\n", dockerCredentialMagicConfig)
 		os.Exit(1)
 	}
-	if info, err := os.Stat(parentDirAbs); err == nil && info.IsDir() {
-		fmt.Printf("Directory '%s' already exists. Skipping.\n", parentDirAbs)
+	parentDir := filepath.Join(dockerCredentialMagicConfigDirAbs, constants.MappingsSubdir)
+	if info, err := os.Stat(parentDir); err == nil && info.IsDir() {
+		fmt.Printf("Directory '%s' already exists. Skipping.\n", parentDir)
 	} else {
-		fmt.Printf("Creating directory '%s' ...\n", parentDirAbs)
-		if err := os.MkdirAll(parentDirAbs, 0755); err != nil {
+		fmt.Printf("Creating directory '%s' ...\n", parentDir)
+		if err := os.MkdirAll(parentDir, 0755); err != nil {
 			fmt.Printf("Error creating directory: %s\n", err.Error())
 			os.Exit(1)
 		}
@@ -168,7 +166,7 @@ func subcommandInit() {
 		os.Exit(1)
 	}
 	for _, item := range items {
-		filename := filepath.Join(parentDirAbs, item.Name())
+		filename := filepath.Join(parentDir, item.Name())
 		if _, err := os.Stat(filename); err == nil {
 			fmt.Printf("File '%s' already exists. Skipping.\n", filename)
 			continue
@@ -191,6 +189,17 @@ func subcommandInit() {
 			os.Exit(1)
 		}
 	}
+	magicConfig := filepath.Join(dockerCredentialMagicConfigDirAbs, constants.DockerConfigFileBasename)
+	if _, err := os.Stat(magicConfig); err == nil {
+		fmt.Printf("File '%s' already exists. Skipping.\n", magicConfig)
+	} else {
+		fmt.Printf("Creating magic config file '%s' ...\n", magicConfig)
+		err := ioutil.WriteFile(magicConfig, []byte(constants.DockerConfigFileContents), 0644)
+		if err != nil {
+			fmt.Printf("Error writing magic config file %s: %s\n", magicConfig, err.Error())
+			os.Exit(1)
+		}
+	}
 	os.Exit(0)
 }