use opportunistic reflink for copying files

Author: thisguycodes

go.mod

@@ -95,6 +95,7 @@ require (
 	github.com/mattn/go-shellwords v1.0.12
 	github.com/spf13/afero v1.15.0
 	github.com/testcontainers/testcontainers-go v0.41.0
+	github.com/thisguycodes/copy v0.0.0-20260330081957-1daf4a9cab34
 	github.com/wI2L/jsondiff v0.7.0
 	github.com/xeipuuv/gojsonschema v1.2.0
 	go.uber.org/mock v0.6.0

go.sum

@@ -954,6 +954,8 @@ github.com/tencentcloud/tencentcloud-sdk-go v0.0.0-20190816164403-f8fa457a3c72/g
 github.com/tencentyun/cos-go-sdk-v5 v0.0.0-20190808065407-f07404cefc8c/go.mod h1:wk2XFUg6egk4tSDNZtXeKfe2G6690UVyt163PuUxBZk=
 github.com/testcontainers/testcontainers-go v0.41.0 h1:mfpsD0D36YgkxGj2LrIyxuwQ9i2wCKAD+ESsYM1wais=
 github.com/testcontainers/testcontainers-go v0.41.0/go.mod h1:pdFrEIfaPl24zmBjerWTTYaY0M6UHsqA1YSvsoU40MI=
+github.com/thisguycodes/copy v0.0.0-20260330081957-1daf4a9cab34 h1:W5GGkFs0Dcv1COvDOi+9MGzcqlQwkVKVS/+tArz8TDo=
+github.com/thisguycodes/copy v0.0.0-20260330081957-1daf4a9cab34/go.mod h1:+SwikrVoNbN+m/M0bR7NrfWUF/bMSQAZlcZMaMOUCmc=
 github.com/tidwall/gjson v1.14.2/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/gjson v1.18.0 h1:FIDeeyB800efLX89e5a8Y0BNH+LOngJyGrIWxG2FKQY=
 github.com/tidwall/gjson v1.18.0/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=

internal/util/file.go

@@ -21,6 +21,7 @@ import (
 	"github.com/gruntwork-io/terragrunt/pkg/log"
 	"github.com/mattn/go-zglob"
 	"github.com/mitchellh/go-homedir"
+	"github.com/thisguycodes/copy"
 )
 
 const (
@@ -504,13 +505,7 @@ func TerragruntExcludes(path string) bool {
 
 // CopyFile copies a file from source to destination.
 func CopyFile(source string, destination string) error {
-	file, err := os.Open(source)
-	if err != nil {
-		return errors.New(err)
-	}
-	defer file.Close()
-
-	return WriteFileWithSamePermissions(source, destination, file)
+	return copy.Copy(source, destination)
 }
 
 // WriteFileWithSamePermissions writes a file to the given destination with the given contents