inventory_directory option for ansible provisioner

Add an `inventory_directory` setting to the Ansible provisioner that
allows a user to specify a directory in which the Packer Ansible
provisioner would write the generated inventory file.  If a value is
specified for this setting, then have the Packer Ansible provisioner
pass this directory as the -i arg when it calls ansible.

This would allow an Ansible playbook used by the Packer Ansible
provisioner to use variables specified in `host_vars` and `group_vars`
in this inventory directory.

provisioner/ansible/provisioner.go

@@ -53,6 +53,7 @@ type Config struct {
 	SSHAuthorizedKeyFile string   `mapstructure:"ssh_authorized_key_file"`
 	SFTPCmd              string   `mapstructure:"sftp_command"`
 	UseSFTP              bool     `mapstructure:"use_sftp"`
+	InventoryDirectory   string   `mapstructure:"inventory_directory"`
 	inventoryFile        string
 }
 
@@ -249,7 +250,7 @@ func (p *Provisioner) Provision(ui packer.Ui, comm packer.Communicator) error {
 	go p.adapter.Serve()
 
 	if len(p.config.inventoryFile) == 0 {
-		tf, err := ioutil.TempFile("", "packer-provisioner-ansible")
+		tf, err := ioutil.TempFile(p.config.InventoryDirectory, "packer-provisioner-ansible")
 		if err != nil {
 			return fmt.Errorf("Error preparing inventory file: %s", err)
 		}
@@ -300,9 +301,16 @@ func (p *Provisioner) Cancel() {
 	os.Exit(0)
 }
 
+func (p *Provisioner) getInventoryArg() string {
+	if len(p.config.InventoryDirectory) != 0 {
+		return p.config.InventoryDirectory
+	}
+	return p.config.inventoryFile
+}
+
 func (p *Provisioner) executeAnsible(ui packer.Ui, comm packer.Communicator, privKeyFile string) error {
 	playbook, _ := filepath.Abs(p.config.PlaybookFile)
-	inventory := p.config.inventoryFile
+	inventory := p.getInventoryArg()
 	var envvars []string
 
 	args := []string{playbook, "-i", inventory}

provisioner/ansible/provisioner_test.go

@@ -76,6 +76,12 @@ func TestProvisionerPrepare_Defaults(t *testing.T) {
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
+
+	config["inventory_directory"] = "some_directory"
+	err = p.Prepare(config)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
 }
 
 func TestProvisionerPrepare_PlaybookFile(t *testing.T) {
@@ -246,6 +252,55 @@ func TestProvisionerPrepare_LocalPort(t *testing.T) {
 	}
 }
 
+func TestProvisioner_getInventoryArg(t *testing.T) {
+	var p Provisioner
+	config := testConfig(t)
+	defer os.Remove(config["command"].(string))
+
+	hostkey_file, err := ioutil.TempFile("", "hostkey")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Remove(hostkey_file.Name())
+
+	publickey_file, err := ioutil.TempFile("", "publickey")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Remove(publickey_file.Name())
+
+	playbook_file, err := ioutil.TempFile("", "playbook")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Remove(playbook_file.Name())
+
+	config["ssh_host_key_file"] = hostkey_file.Name()
+	config["ssh_authorized_key_file"] = publickey_file.Name()
+	config["playbook_file"] = playbook_file.Name()
+
+	err = p.Prepare(config)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	p.config.inventoryFile = "somefile"
+	if p.getInventoryArg() != "somefile" {
+		t.Fatal("getInventoryArg should return inventoryFile if InventoryDirectory is not set.")
+	}
+
+	// Uses InventoryDirectory if set
+	config["inventory_directory"] = "somedirectory"
+	err = p.Prepare(config)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if p.getInventoryArg() != "somedirectory" {
+		t.Fatal("getInventoryArg should return InventoryDirectory if InventoryDirectory is set.")
+	}
+}
+
 func TestAnsibleGetVersion(t *testing.T) {
 	if os.Getenv("PACKER_ACC") == "" {
 		t.Skip("This test is only run with PACKER_ACC=1 and it requires Ansible to be installed")

website/source/docs/provisioners/ansible.html.md

@@ -113,6 +113,15 @@ Optional Parameters:
 - `user` (string) - The `ansible_user` to use. Defaults to the user running
   packer.
 
+- `inventory_directory` (string) - The directory in which to place the
+  generated ansible inventory file. If this is specified, then this directory
+  is what will get passed to the `-i` argument of the `ansible` command when
+  this provisioner runs Ansible.  By default, the generated ansible inventory
+  will be placed in a temporary file in the system-specific temporary file
+  location, and the fully-qualified name of this temporary file will be passed
+  to the `-i` argument of the `ansible` command when this provisioner runs
+  ansible.
+
 ## Limitations
 
 ### Redhat / CentOS