dockerfile: graduate ADD <git ref> from labs

e.g., `ADD https://github.com/moby/buildkit.git#v0.10.1 /buildkit`

Introduced to dockerfile:1.5-labs in PR 2799

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

.golangci.yml

@@ -7,7 +7,6 @@ run:
 
   build-tags:
     - dfrunsecurity
-    - dfaddgit
     - dfaddchecksum
 
 linters:

frontend/dockerfile/dockerfile2llb/convert.go

@@ -1082,9 +1082,6 @@ func dispatchCopy(d *dispatchState, cfg copyConfig) error {
 			if !cfg.isAddCommand {
 				return errors.New("source can't be a git ref for COPY")
 			}
-			if !addGitEnabled {
-				return errors.New("instruction ADD <git ref> requires the labs channel")
-			}
 			// TODO: print a warning (not an error) if gitRef.UnencryptedTCP is true
 			commit := gitRef.Commit
 			if gitRef.SubDir != "" {

frontend/dockerfile/dockerfile2llb/convert_addgit.go

@@ -1,6 +1,3 @@
-//go:build dfaddgit
-// +build dfaddgit
-
 package dockerfile
 
 import (

frontend/dockerfile/dockerfile2llb/convert_noaddgit.go

@@ -1312,6 +1312,7 @@ The `--checksum` flag only supports HTTP sources currently.
 > **Note**
 >
 > Not yet available in stable syntax, use [`docker/dockerfile:1-labs`](#syntax) version (`1.5-labs` or newer).
+> Planned to be included in `docker/dockerfile:1.6`.
 
 This form allows adding a git repository to an image directly, without using the `git` command inside the image:
 ```

frontend/dockerfile/dockerfile_addgit_test.go

@@ -1 +1 @@
-dfrunsecurity dfaddgit dfaddchecksum
+dfrunsecurity dfaddchecksum