packer: add `pwd` function with working directory [GH-762]

CHANGELOG.md

@@ -41,6 +41,8 @@ IMPROVEMENTS:
   dramatically increased.
 * core: Build names are now template processed so you can use things
   like user variables in them. [GH-744]
+* core: New "pwd" function available globally that returns the working
+  directory. [GH-762]
 * builder/amazon/all: Launched EC2 instances now have a name of
   "Packer Builder" so that they are easily recognizable. [GH-642]
 * builder/amazon/all: Copying AMIs to multiple regions now happens

packer/config_template.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"github.com/mitchellh/packer/common/uuid"
+	"os"
 	"strconv"
 	"text/template"
 	"time"
@@ -36,6 +37,7 @@ func NewConfigTemplate() (*ConfigTemplate, error) {
 
 	result.root = template.New("configTemplateRoot")
 	result.root.Funcs(template.FuncMap{
+		"pwd":       templatePwd,
 		"isotime":   templateISOTime,
 		"timestamp": templateTimestamp,
 		"user":      result.templateUser,
@@ -97,6 +99,10 @@ func templateISOTime() string {
 	return time.Now().UTC().Format(time.RFC3339)
 }
 
+func templatePwd() (string, error) {
+	return os.Getwd()
+}
+
 func templateTimestamp() string {
 	return strconv.FormatInt(InitTime.Unix(), 10)
 }

packer/config_template_test.go

@@ -2,6 +2,7 @@ package packer
 
 import (
 	"math"
+	"os"
 	"strconv"
 	"testing"
 	"time"
@@ -29,6 +30,27 @@ func TestConfigTemplateProcess_isotime(t *testing.T) {
 	}
 }
 
+func TestConfigTemplateProcess_pwd(t *testing.T) {
+	tpl, err := NewConfigTemplate()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	pwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	result, err := tpl.Process(`{{pwd}}`, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if result != pwd {
+		t.Fatalf("err: %s", result)
+	}
+}
+
 func TestConfigTemplateProcess_timestamp(t *testing.T) {
 	tpl, err := NewConfigTemplate()
 	if err != nil {

website/source/docs/templates/configuration-templates.html.markdown

@@ -53,8 +53,10 @@ While some configuration settings have local variables specific to only that
 configuration, a set of functions are available globally for use in _any string_
 in Packer templates. These are listed below for reference.
 
-* ``isotime`` - UTC time in RFC-3339 format.
-* ``timestamp`` - The current Unix timestamp in UTC.
+* `pwd` - The working directory while executing Packer.
+* `isotime` - UTC time in RFC-3339 format.
+* `timestamp` - The current Unix timestamp in UTC.
+* `uuid` - Returns a random UUID.
 
 ## Amazon Specific Functions