Add pwd function to HCL

Signed-off-by: Jeremiah Snapp <jeremiah@chef.io>

hcl2template/function/pwd.go

@@ -0,0 +1,20 @@
+package function
+
+import (
+	"os"
+
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/function"
+)
+
+// MakePwdFunc constructs a function that returns the working directory as a string.
+func MakePwdFunc() function.Function {
+	return function.New(&function.Spec{
+		Params: []function.Parameter{},
+		Type:   function.StaticReturnType(cty.String),
+		Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
+			dir, err := os.Getwd()
+			return cty.StringVal(dir), err
+		},
+	})
+}

hcl2template/functions.go

@@ -76,6 +76,7 @@ func Functions(basedir string) map[string]function.Function {
 		"parseint":        stdlib.ParseIntFunc,
 		"pathexpand":      filesystem.PathExpandFunc,
 		"pow":             stdlib.PowFunc,
+		"pwd":             pkrfunction.MakePwdFunc(),
 		"range":           stdlib.RangeFunc,
 		"reverse":         stdlib.ReverseFunc,
 		"replace":         stdlib.ReplaceFunc,

website/data/docs-navigation.js

@@ -112,6 +112,7 @@ export default [
               'fileexists',
               'fileset',
               'pathexpand',
+              'pwd',
             ],
           },
           {

website/pages/docs/from-1.5/functions/file/pwd.mdx

@@ -0,0 +1,21 @@
+---
+layout: docs
+page_title: pwd - Functions - Configuration Language
+sidebar_title: pwd
+description: The pwd function returns the working directory while executing Packer.
+---
+
+# `pwd` Function
+
+`pwd` returns the working directory while executing Packer.
+
+```hcl
+pwd()
+```
+
+## Examples
+
+```shell-session
+> pwd()
+/home/user/some/packer
+```