Fix handling of Debian files with trailing slash (#26087)

Fixes #26022

- Fix handling of files with trailing slash
- Fix handling of duplicate package file errors
- Added test for both

modules/packages/debian/metadata.go

@@ -80,7 +80,9 @@ func ParsePackage(r io.Reader) (*Package, error) {
 
 		if strings.HasPrefix(hd.Name, controlTar) {
 			var inner io.Reader
-			switch hd.Name[len(controlTar):] {
+			// https://man7.org/linux/man-pages/man5/deb-split.5.html#FORMAT
+			// The file names might contain a trailing slash (since dpkg 1.15.6).
+			switch strings.TrimSuffix(hd.Name[len(controlTar):], "/") {
 			case "":
 				inner = arr
 			case ".gz":

modules/packages/debian/metadata_test.go

@@ -69,59 +69,73 @@ func TestParsePackage(t *testing.T) {
 		tw.Write([]byte("Package: gitea\nVersion: 1.0.0\nArchitecture: amd64\n"))
 		tw.Close()
 
-		t.Run("None", func(t *testing.T) {
-			data := createArchive(map[string][]byte{"control.tar": buf.Bytes()})
+		cases := []struct {
+			Extension     string
+			WriterFactory func(io.Writer) io.WriteCloser
+		}{
+			{
+				Extension: "",
+				WriterFactory: func(w io.Writer) io.WriteCloser {
+					return nopCloser{w}
+				},
+			},
+			{
+				Extension: ".gz",
+				WriterFactory: func(w io.Writer) io.WriteCloser {
+					return gzip.NewWriter(w)
+				},
+			},
+			{
+				Extension: ".xz",
+				WriterFactory: func(w io.Writer) io.WriteCloser {
+					xw, _ := xz.NewWriter(w)
+					return xw
+				},
+			},
+			{
+				Extension: ".zst",
+				WriterFactory: func(w io.Writer) io.WriteCloser {
+					zw, _ := zstd.NewWriter(w)
+					return zw
+				},
+			},
+		}
 
-			p, err := ParsePackage(data)
-			assert.NotNil(t, p)
-			assert.NoError(t, err)
-			assert.Equal(t, "gitea", p.Name)
-		})
+		for _, c := range cases {
+			t.Run(c.Extension, func(t *testing.T) {
+				var cbuf bytes.Buffer
+				w := c.WriterFactory(&cbuf)
+				w.Write(buf.Bytes())
+				w.Close()
 
-		t.Run("gz", func(t *testing.T) {
-			var zbuf bytes.Buffer
-			zw := gzip.NewWriter(&zbuf)
-			zw.Write(buf.Bytes())
-			zw.Close()
+				data := createArchive(map[string][]byte{"control.tar" + c.Extension: cbuf.Bytes()})
 
-			data := createArchive(map[string][]byte{"control.tar.gz": zbuf.Bytes()})
+				p, err := ParsePackage(data)
+				assert.NotNil(t, p)
+				assert.NoError(t, err)
+				assert.Equal(t, "gitea", p.Name)
 
-			p, err := ParsePackage(data)
-			assert.NotNil(t, p)
-			assert.NoError(t, err)
-			assert.Equal(t, "gitea", p.Name)
-		})
+				t.Run("TrailingSlash", func(t *testing.T) {
+					data := createArchive(map[string][]byte{"control.tar" + c.Extension + "/": cbuf.Bytes()})
 
-		t.Run("xz", func(t *testing.T) {
-			var xbuf bytes.Buffer
-			xw, _ := xz.NewWriter(&xbuf)
-			xw.Write(buf.Bytes())
-			xw.Close()
-
-			data := createArchive(map[string][]byte{"control.tar.xz": xbuf.Bytes()})
-
-			p, err := ParsePackage(data)
-			assert.NotNil(t, p)
-			assert.NoError(t, err)
-			assert.Equal(t, "gitea", p.Name)
-		})
-
-		t.Run("zst", func(t *testing.T) {
-			var zbuf bytes.Buffer
-			zw, _ := zstd.NewWriter(&zbuf)
-			zw.Write(buf.Bytes())
-			zw.Close()
-
-			data := createArchive(map[string][]byte{"control.tar.zst": zbuf.Bytes()})
-
-			p, err := ParsePackage(data)
-			assert.NotNil(t, p)
-			assert.NoError(t, err)
-			assert.Equal(t, "gitea", p.Name)
-		})
+					p, err := ParsePackage(data)
+					assert.NotNil(t, p)
+					assert.NoError(t, err)
+					assert.Equal(t, "gitea", p.Name)
+				})
+			})
+		}
 	})
 }
 
+type nopCloser struct {
+	io.Writer
+}
+
+func (nopCloser) Close() error {
+	return nil
+}
+
 func TestParseControlFile(t *testing.T) {
 	buildContent := func(name, version, architecture string) *bytes.Buffer {
 		var buf bytes.Buffer