fix: md5sums entries and lintian errors/warnings

Missing trailing ./ in md5sums for changelog.Debian.gz caused
md5sums-lists-nonexistent-file and file-missing-in-md5sums
and is fixed using files.AsExplicitRelativePath.
Adding copyright file fixes no-copyright-file.
Set file_info fixes executable-is-not-world-readable,
non-standard-executable-perm, non-standard-file-perm.
Adding section fixes unknown-section, empty-field.
Using standard compress/gzip module fixes
package-contains-timestamped-gzip,
because klauspost/pgzip does not support empty mod time.
Adding urgency and distribution in changelog fixes
syntax-error-in-debian-changelog.
Adding mail address to maintainer fixes malformed-contact.
Correcting description fixes description-starts-with-package-name
and description-starts-with-leading-spaces.

deb/deb.go

@@ -4,6 +4,7 @@ package deb
 import (
 	"archive/tar"
 	"bytes"
+	"compress/gzip"
 	"crypto/md5" // nolint:gas
 	"crypto/sha1"
 	"errors"
@@ -22,7 +23,6 @@ import (
 	"github.com/goreleaser/nfpm/v2/files"
 	"github.com/goreleaser/nfpm/v2/internal/sign"
 	"github.com/klauspost/compress/zstd"
-	gzip "github.com/klauspost/pgzip"
 	"github.com/ulikunitz/xz"
 )
 
@@ -454,6 +454,9 @@ func createChangelogInsideDataTar(tarw *tar.Writer, g io.Writer, info *nfpm.Info
 	fileName string,
 ) (int64, error) {
 	var buf bytes.Buffer
+	// we need here a non timestamped compression -> https://github.com/klauspost/pgzip doesn't support that
+	// https://github.com/klauspost/pgzip/blob/v1.2.6/gzip.go#L322 vs.
+	// https://cs.opensource.google/go/go/+/refs/tags/go1.20.4:src/compress/gzip/gzip.go;l=157
 	out, err := gzip.NewWriterLevel(&buf, gzip.BestCompression)
 	if err != nil {
 		return 0, fmt.Errorf("could not create gzip writer: %w", err)
@@ -482,7 +485,7 @@ func createChangelogInsideDataTar(tarw *tar.Writer, g io.Writer, info *nfpm.Info
 		return 0, err
 	}
 
-	if _, err = fmt.Fprintf(g, "%x  %s\n", digest.Sum(nil), fileName); err != nil {
+	if _, err = fmt.Fprintf(g, "%x  %s\n", digest.Sum(nil), files.AsExplicitRelativePath(fileName)); err != nil {
 		return 0, err
 	}
 

testdata/acceptance/core.withchangelog.yaml

@@ -4,16 +4,25 @@ platform: "linux"
 changelog: "./testdata/changelog.yaml"
 version: "v1.2.3"
 release: "simple"
-maintainer: "Foo Bar"
+maintainer: "Foo Bar <foo@example.org>"
 description: |
-  Foo bar
-    Multiple lines
+  Program foo bar
+  Multiple lines
 vendor: "foobar"
 homepage: "https://foobar.org"
 license: "MIT"
+section: misc
 contents:
 - src: ./testdata/fake
   dst: /usr/bin/fake
+  file_info:
+    mode: 0755
 - src: ./testdata/whatever.conf
   dst: /etc/foo/whatever.conf
   type: config
+  file_info:
+    mode: 0644
+- src: ./testdata/copyright
+  dst: /usr/share/doc/foo/
+  file_info:
+    mode: 0644

testdata/acceptance/deb.dockerfile

@@ -140,8 +140,20 @@ RUN lintian /tmp/foo.deb > lintian.out
 RUN test $(grep -c 'debian-changelog-file-missing-or-wrong-name' lintian.out) = 0
 RUN test $(grep -c 'changelog-not-compressed-with-max-compression' lintian.out) = 0
 RUN test $(grep -c 'unknown-control-file' lintian.out) = 0
-# TODO: RUN test $(grep -c 'package-contains-timestamped-gzip' lintian.out) = 0
-# TODO: RUN test $(grep -c 'syntax-error-in-debian-changelog' lintian.out) = 0
+RUN test $(grep -c 'package-contains-timestamped-gzip' lintian.out) = 0
+RUN test $(grep -c 'md5sums-lists-nonexistent-file' lintian.out) = 0
+RUN test $(grep -c 'file-missing-in-md5sums' lintian.out) = 0
+RUN test $(grep -c 'syntax-error-in-debian-changelog' lintian.out) = 0
+RUN test $(grep -c 'no-copyright-file' lintian.out) = 0
+RUN test $(grep -c 'executable-is-not-world-readable' lintian.out) = 0
+RUN test $(grep -c 'non-standard-executable-perm' lintian.out) = 0
+RUN test $(grep -c 'non-standard-file-perm' lintian.out) = 0
+RUN test $(grep -c 'unknown-section' lintian.out) = 0
+RUN test $(grep -c 'empty-field' lintian.out) = 0
+RUN test $(grep -c 'syntax-error-in-debian-changelog' lintian.out) = 0
+RUN test $(grep -c 'malformed-contact' lintian.out) = 0
+RUN test $(grep -c 'description-starts-with-package-name' lintian.out) = 0
+RUN test $(grep -c 'description-starts-with-leading-spaces' lintian.out) = 0
 
 # ---- rules test ----
 FROM min AS rules

testdata/changelog.yaml

@@ -1,4 +1,8 @@
-- semver: "1.1.0-1"
+- deb:
+    urgency: medium
+    distributions:
+      - bookworm
+  semver: "1.1.0-1"
   date: "2009-12-08T22:00:00Z"
   packager: "Carlos A Becker <pkg@carlosbecker.com>"
   urgency: "low"
@@ -7,7 +11,11 @@
     - note: "note 1"
     - note: "note 2"
 
-- semver: "1.0.0-1"
+- deb:
+    urgency: medium
+    distributions:
+      - bookworm
+  semver: "1.0.0-1"
   date: "2009-11-10T23:00:00Z"
   packager: "Carlos A Becker <pkg@carlosbecker.com>"
   urgency: "low"

testdata/copyright

@@ -0,0 +1,5 @@
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Files:
+ *
+Copyright: 2023 The foo bar
+License: MIT