Add support for zstd compression (Closes: #1010465)

debian/patches/zstd.patch

@@ -0,0 +1,45 @@
+Description: Add support for zst compression
+Origin: https://github.com/aptly-dev/aptly/pull/1050/files/e686753656b340abbb80c593f43879bfc9806cfd
+Reviewed-By: Anton Gladky <gladk@debian.org>
+Last-Update: 2022-04-29
+
+Index: aptly/deb/deb.go
+===================================================================
+--- aptly.orig/deb/deb.go
++++ aptly/deb/deb.go
+@@ -16,6 +16,7 @@ import (
+ 
+ 	"github.com/aptly-dev/aptly/pgp"
+ 	"github.com/kjk/lzma"
++	"github.com/klauspost/compress/zstd"
+ 	"github.com/smira/go-xz"
+ )
+ 
+@@ -74,6 +75,13 @@ func GetControlFileFromDeb(packageFile s
+ 				}
+ 				defer unxz.Close()
+ 				tarInput = unxz
++			case "control.tar.zst":
++				unzstd, err := zstd.NewReader(bufReader)
++				if err != nil {
++					return nil, errors.Wrapf(err, "unable to unzstd %s from %s", header.Name, packageFile)
++				}
++				defer unzstd.Close()
++				tarInput = unzstd
+ 			default:
+ 				return nil, fmt.Errorf("unsupported tar compression in %s: %s", packageFile, header.Name)
+ 			}
+@@ -189,6 +197,13 @@ func GetContentsFromDeb(file io.Reader,
+ 				unlzma := lzma.NewReader(bufReader)
+ 				defer unlzma.Close()
+ 				tarInput = unlzma
++			case "data.tar.zst":
++				unzstd, err := zstd.NewReader(bufReader)
++				if err != nil {
++					return nil, errors.Wrapf(err, "unable to unzstd %s from %s", header.Name, packageFile)
++				}
++				defer unzstd.Close()
++				tarInput = unzstd
+ 			default:
+ 				return nil, fmt.Errorf("unsupported tar compression in %s: %s", packageFile, header.Name)
+ 			}