manifest/push: add support for --add-compression

Adds support for `--add-compression` which accepts multiple compression
formats and when used it will add all instances in a manifest list with
requested compression formats.

Signed-off-by: Aditya R <[email protected]>

cmd/buildah/manifest.go

@@ -227,6 +227,7 @@ func init() {
 	flags.StringVar(&manifestPushOpts.creds, "creds", "", "use `[username[:password]]` for accessing the registry")
 	flags.StringVar(&manifestPushOpts.digestfile, "digestfile", "", "after copying the image, write the digest of the resulting digest to the file")
 	flags.StringVarP(&manifestPushOpts.format, "format", "f", "", "manifest type (oci or v2s2) to attempt to use when pushing the manifest list (default is manifest type of source)")
+	flags.StringSliceVar(&manifestPushOpts.addCompression, "add-compression", nil, "add instances with selected compression while pushing")
 	flags.BoolVarP(&manifestPushOpts.removeSignatures, "remove-signatures", "", false, "don't copy signatures when pushing images")
 	flags.StringVar(&manifestPushOpts.signBy, "sign-by", "", "sign the image using a GPG key with the specified `FINGERPRINT`")
 	flags.StringVar(&manifestPushOpts.signaturePolicy, "signature-policy", "", "`pathname` of signature policy file (not usually used)")
@@ -908,6 +909,7 @@ func manifestPush(systemContext *types.SystemContext, store storage.Store, listI
 		RemoveSignatures:   opts.removeSignatures,
 		SignBy:             opts.signBy,
 		ManifestType:       manifestType,
+		AddCompression:     opts.addCompression,
 	}
 	if opts.all {
 		options.ImageListSelection = cp.CopyAllImages

cmd/buildah/push.go

@@ -46,6 +46,7 @@ type pushOptions struct {
 	encryptionKeys     []string
 	encryptLayers      []int
 	insecure           bool
+	addCompression     []string
 }
 
 func init() {

docs/buildah-manifest-push.1.md

@@ -18,6 +18,15 @@ The list image's ID and the digest of the image's manifest.
 
 ## OPTIONS
 
+**--add-compression** *compression*
+
+Makes sure that requested compression variant for each platform is added to the manifest list keeping original instance
+intact in the same manifest list. Supported values are (`gzip`, `zstd` and `zstd:chunked`)
+
+Note: This is different than `--compression` which replaces the instance with requested with specified compression
+while `--add-compression` makes sure than each instance has it variant added to manifest list without modifying the
+original instance.
+
 **--all**
 
 Push the images mentioned in the manifest list or image index, in addition to

tests/bud.bats

@@ -11,6 +11,34 @@ load helpers
   run_buildah build $BUDFILES/stdio
 }
 
+@test "bud: build manifest list and --add-compression zstd" {
+  local contextdir=${TEST_SCRATCH_DIR}/bud/platform
+  mkdir -p $contextdir
+
+  cat > $contextdir/Dockerfile1 << _EOF
+FROM alpine
+_EOF
+
+  start_registry
+  run_buildah login --tls-verify=false --authfile ${TEST_SCRATCH_DIR}/test.auth --username testuser --password testpassword localhost:${REGISTRY_PORT}
+  run_buildah build $WITH_POLICY_JSON -t image1 --platform linux/amd64 -f $contextdir/Dockerfile1
+  run_buildah build $WITH_POLICY_JSON -t image2 --platform linux/arm64 -f $contextdir/Dockerfile1
+
+  run_buildah manifest create foo
+  run_buildah manifest add foo image1
+  run_buildah manifest add foo image2
+
+  run_buildah manifest push $WITH_POLICY_JSON --authfile ${TEST_SCRATCH_DIR}/test.auth --all --add-compression zstd --tls-verify=false foo docker://localhost:${REGISTRY_PORT}/list
+
+  run_buildah manifest inspect --authfile ${TEST_SCRATCH_DIR}/test.auth --tls-verify=false localhost:${REGISTRY_PORT}/list
+  list="$output"
+
+  validate_instance_compression "0" "$list" "amd64" "gzip"
+  validate_instance_compression "1" "$list" "arm64" "gzip"
+  validate_instance_compression "2" "$list" "amd64" "zstd"
+  validate_instance_compression "3" "$list" "arm64" "zstd"
+}
+
 @test "bud with --dns* flags" {
   _prefetch alpine
 
@@ -2103,6 +2131,39 @@ function _test_http() {
   run_buildah from ${target}
 }
 
+# Helper function for several of the tests which verifies compression.
+#
+#  Usage:  validate_instance_compression INDEX MANIFEST ARCH COMPRESSION
+#
+#     INDEX             instance which needs to be verified in
+#                       provided manifest list.
+#
+#     MANIFEST          OCI manifest specification in json format
+#
+#     ARCH              instance architecture
+#
+#     COMPRESSION       compression algorithm name; e.g "zstd".
+#
+function validate_instance_compression {
+  case $4 in
+
+   gzip)
+    run jq -r '.manifests['$1'].annotations' <<< $2
+    # annotation is `null` for gzip compression
+    assert "$output" = "null" ".manifests[$1].annotations (null means gzip)"
+    ;;
+
+  zstd)
+    # annotation `'"io.github.containers.compression.zstd": "true"'` must be there for zstd compression
+    run jq -r '.manifests['$1'].annotations."io.github.containers.compression.zstd"' <<< $2
+    assert "$output" = "true" ".manifests[$1].annotations.'io.github.containers.compression.zstd' (io.github.containers.compression.zstd must be set)"
+    ;;
+  esac
+
+  run jq -r '.manifests['$1'].platform.architecture' <<< $2
+  assert "$output" = $3 ".manifests[$1].platform.architecture"
+}
+
 @test "bud-http-Dockerfile" {
   _test_http from-scratch Containerfile
 }