make package_include match output_vagrantfile parsing and abspath calculation

builder/vagrant/builder.go

@@ -125,9 +125,12 @@ type Config struct {
 	AddInsecure bool `mapstructure:"add_insecure" required:"false"`
 	// if true, Packer will not call vagrant package to
 	// package your base box into its own standalone .box file.
-	SkipPackage       bool     `mapstructure:"skip_package" required:"false"`
+	SkipPackage       bool   `mapstructure:"skip_package" required:"false"`
-	OutputVagrantfile string   `mapstructure:"output_vagrantfile"`
+	OutputVagrantfile string `mapstructure:"output_vagrantfile"`
-	PackageInclude    []string `mapstructure:"package_include"`
+	// Equivalent to setting the
+	// [`--include`](https://www.vagrantup.com/docs/cli/package.html#include-x-y-z) option
+	// in `vagrant package`; defaults to unset
+	PackageInclude []string `mapstructure:"package_include"`
 
 	ctx interpolate.Context
 }
@@ -193,6 +196,19 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, []string, error) {
 		}
 	}
 
+	if len(b.config.PackageInclude) > 0 {
+		include := []string{}
+		for i, inclFile := range b.config.PackageInclude {
+			b.config.PackageInclude, err = filepath.Abs(b.config.PackageInclude)
+			if err != nil {
+				packer.MultiErrorAppend(errs,
+					fmt.Errorf("unable to determine absolute path for file to be included: %s", inclFile))
+			}
+			include = append(include, inclFile)
+		}
+		b.config.PackageInclude = include
+	}
+
 	if b.config.TeardownMethod == "" {
 		// If we're using a box that's already opened on the system, don't
 		// automatically destroy it. If we open the box ourselves, then go ahead