feat: include non-conventional headers in payload for git signatures (#9558)

This patch is meant to fix #8255, by adding all (even unknown) git commit headers to the payload.

Unit test is added.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/9558
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Gabor Pihaj <gabor.pihaj@gmail.com>
Co-committed-by: Gabor Pihaj <gabor.pihaj@gmail.com>

modules/git/commit_reader.go

@@ -24,6 +24,7 @@ func CommitFromReader(gitRepo *Repository, objectID ObjectID, reader io.Reader)
 	payloadSB := new(strings.Builder)
 	signatureSB := new(strings.Builder)
 	messageSB := new(strings.Builder)
+	firstLine := true
 	message := false
 	pgpsig := false
 
@@ -83,21 +84,25 @@ readLoop:
 				commit.Committer = &Signature{}
 				commit.Committer.Decode(data)
 				_, _ = payloadSB.Write(line)
-			case "encoding":
-				_, _ = payloadSB.Write(line)
-			case "change-id": // jj-vcs specific header.
-				_, _ = payloadSB.Write(line)
 			case "gpgsig":
 				fallthrough
 			case "gpgsig-sha256": // FIXME: no intertop, so only 1 exists at present.
 				_, _ = signatureSB.Write(data)
 				_ = signatureSB.WriteByte('\n')
 				pgpsig = true
+			default:
+				// If the first line is not any of the known headers, then it is probably the prefix added when git cat-file is called with --batch, and that is not part of the payload
+				if !firstLine {
+					// Every subsequent header field is added to the payload
+					_, _ = payloadSB.Write(line)
+				}
 			}
 		} else {
 			_, _ = messageSB.Write(line)
 			_, _ = payloadSB.Write(line)
 		}
+
+		firstLine = false
 	}
 	commit.CommitMessage = messageSB.String()
 	commit.Signature = &ObjectSignature{

modules/git/commit_test.go

@@ -239,6 +239,77 @@ January where the year starts on a Monday :)`, commitFromReader.Signature.Payloa
 	assert.Equal(t, "Nicole Patricia Mazzuca <nicole@strega-nil.co>", commitFromReader.Author.String())
 }
 
+func TestGitbutlerCustomHeaderFields(t *testing.T) {
+	// example from: https://github.com/go-gitea/gitea/issues/34529#issuecomment-2908481092
+	commitString := `tree a29321bf9e3ec433ed9e47b1cbbac6906c71fc60
+parent c0d83043ade7fa3ca10659608799477e9daa670b
+author Sebastian Thiel <sebastian.thiel@icloud.com> 1747920681 +0200
+committer Sebastian Thiel <sebastian.thiel@icloud.com> 1748010747 +0200
+gitbutler-headers-version 2
+gitbutler-change-id 1063f7ea-d841-43b3-903a-01747681c40d
+gpgsig -----BEGIN PGP SIGNATURE-----
+ 
+ iQIzBAABCAAdFiEE6vnM/NCHZAjyl8YKnLXueJXoJosFAmgwhvsACgkQnLXueJXo
+ JovXUxAAq0WKJILCUAxyhwh5tRdxJTB2NjiCLf+ggLfjyrWPtMWPi/YUt7iGPB2H
+ Wbv9U7l5t+54fPX8TQtBKZ79YaDMfYdjlfDSijmPruf8/MXB4G0rAaIajtCr0usZ
+ kJDOgmmYS7bVMybDe6guwFZappiuSS2dCEYgeJun+q7Y6IYsfvdAluJmGubQIkPT
+ rrEffqoQz3URmDYnAKW3sTRUVwCkYIJDxpl/W0Rvc0jmELdkHu7JYX7XvZBYSUDq
+ FWgzCPjyErtkKk8AqoeWtTCpL+9ozzNIXNRKjGCOL2LG4H/uuNFdM46HB+KW/7+B
+ wMGcpZk8T/zN9Cf348M+y+o09QX1OWavDS6LgvWJaDtG/swgxV96KKR5lEtdd1IU
+ JHuXfPUfGp4r378FIrbPK+Thu5bn9Yq8qGvdZOpTqDxHPU9/o9wLpJghcWJZ5O3X
+ MpK4HdN+bME2zgBd08QsOjANogbJIz9MVaMGRFlCO5iOiz2DxG+v2KkO8IRwGXaO
+ OKKQ7BD04fS2wFma862BaTtB9M9f9UTWV4e2mgRpSDJWTQKrj+HkJ63gAFQYFnfp
+ ppgqZLkmzH1Ta2U56JSMMfOoKVFgjuxRx1d+tzdC+TpQyo06NI1KkNMepK1rhFBW
+ p8hej6n/7Bl9LL/W+DKsNqW9jQbTYu66JqKs3Kg7xga6w/ss0iw=
+ =VG6I
+ -----END PGP SIGNATURE-----
+
+asdf
+asdf
+asdf
+`
+
+	sha := &Sha1Hash{0xe6, 0x69, 0x11, 0x91, 0x44, 0x14, 0xb0, 0xda, 0xa8, 0x5d, 0x4a, 0x42, 0x8c, 0x8d, 0x60, 0x7b, 0x9b, 0x24, 0x9a, 0x2c}
+	gitRepo, err := openRepositoryWithDefaultContext(filepath.Join(testReposDir, "repo1_bare"))
+	require.NoError(t, err)
+	assert.NotNil(t, gitRepo)
+	defer gitRepo.Close()
+
+	commitFromReader, err := CommitFromReader(gitRepo, sha, strings.NewReader(commitString))
+	require.NoError(t, err)
+	require.NotNil(t, commitFromReader)
+	assert.EqualValues(t, sha, commitFromReader.ID)
+	assert.Equal(t, `-----BEGIN PGP SIGNATURE-----
+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+=VG6I
+-----END PGP SIGNATURE-----
+`, commitFromReader.Signature.Signature)
+	assert.Equal(t, `tree a29321bf9e3ec433ed9e47b1cbbac6906c71fc60
+parent c0d83043ade7fa3ca10659608799477e9daa670b
+author Sebastian Thiel <sebastian.thiel@icloud.com> 1747920681 +0200
+committer Sebastian Thiel <sebastian.thiel@icloud.com> 1748010747 +0200
+gitbutler-headers-version 2
+gitbutler-change-id 1063f7ea-d841-43b3-903a-01747681c40d
+
+asdf
+asdf
+asdf
+`, commitFromReader.Signature.Payload)
+	assert.Equal(t, "Sebastian Thiel <sebastian.thiel@icloud.com>", commitFromReader.Author.String())
+}
+
 func TestHasPreviousCommit(t *testing.T) {
 	bareRepo1Path := filepath.Join(testReposDir, "repo1_bare")