[WARNING] unknown commit-graph chunk: 0x47444132

[TheSnoozer]

Version

6.7.0.202309050840-r

Operating System

MacOS

Bug description

When running the git-commit-id-maven-plugin (which uses jgit under the hood) a warning about unknown commit-graph chunk is reported.

This warning seems to only be reproducible under mac using a

Apache Maven 3.9.6 (bc0240f3c744dd6b6ec2920b3cd08dcc295161ae)
Maven home: /Users/khm/tools/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /Users/khm/.sdkman/candidates/java/21.0.1-open
Default locale: en_DE, platform encoding: UTF-8
OS name: "mac os x", version: "14.0", arch: "aarch64", family: "mac"

The message templates are defined in:

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties:commitGraphChunkUnknown=unknown commit-graph chunk: 0x{0}

and the error observed comes from:

jgit/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphLoader.java

Lines 194 to 196 in b1cc74b

	LOG.warn(MessageFormat.format(
	JGitText.get().commitGraphChunkUnknown,
	Integer.toHexString(chunkId)));

.

Actual behavior

When running jgit a warning about an unknown commit-graph chunk is reported:

[INFO] --- git-commit-id:7.0.0:revision (default) @ tree ---
[WARNING] unknown commit-graph chunk: 0x47444132
[WARNING] unknown commit-graph chunk: 0x47444132
[WARNING] unknown commit-graph chunk: 0x47444132
[WARNING] unknown commit-graph chunk: 0x47444132

Expected behavior

No warning.

Relevant log output

No response

Other information

To reproduce checkout the branch https://github.com/khmarbaise/maven-it-extension/tree/git-commit-id-maven-plugin-issue-687
and run mvn clean verify.

Can be reproduced using:

• Maven 4.0.0-alpha-10

Apache Maven 4.0.0-alpha-10 (89d3c0321dda868c432edf504f1884e6fd706f00)
Maven home: /Users/khm/tools/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /Users/khm/.sdkman/candidates/java/21.0.1-open
Default locale: en_DE, platform encoding: UTF-8
OS name: "mac os x", version: "14.0", arch: "aarch64", family: "mac"

• Maven 3.9.6

Apache Maven 3.9.6 (bc0240f3c744dd6b6ec2920b3cd08dcc295161ae)
Maven home: /Users/khm/tools/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /Users/khm/.sdkman/candidates/java/21.0.1-open
Default locale: en_DE, platform encoding: UTF-8
OS name: "mac os x", version: "14.0", arch: "aarch64", family: "mac"

• Maven 3.8.8

mvn --version
Apache Maven 3.8.8 (4c87b05d9aedce574290d1acc98575ed5eb6cd39)
Maven home: /Users/khm/tools/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /Users/khm/.sdkman/candidates/java/21.0.1-open
Default locale: en_DE, platform encoding: UTF-8
OS name: "mac os x", version: "14.0", arch: "aarch64", family: "mac"

Can not be reproduced under linux and the same repository/branch/commit.

original bug-report: git-commit-id/git-commit-id-maven-plugin#687

[TheSnoozer]

I found more context on this.

Jgit's constants are defined here:

jgit/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphConstants.java

Lines 18 to 30 in b1cc74b

	static final int COMMIT_GRAPH_MAGIC = 0x43475048; /* "CGPH" */
	static final int CHUNK_ID_OID_FANOUT = 0x4f494446; /* "OIDF" */
	static final int CHUNK_ID_OID_LOOKUP = 0x4f49444c; /* "OIDL" */
	static final int CHUNK_ID_COMMIT_DATA = 0x43444154; /* "CDAT" */
	static final int CHUNK_ID_EXTRA_EDGE_LIST = 0x45444745; /* "EDGE" */
	static final int CHUNK_ID_BLOOM_FILTER_INDEX = 0x42494458; /* "BIDX" */
	static final int CHUNK_ID_BLOOM_FILTER_DATA = 0x42444154; /* "BDAT" */

This 0x47444132 seems to come from
https://github.com/git/git/blob/a26002b62827b89a19b1084bd75d9371d565d03c/commit-graph.c#L48-L49 and is simply not listed as magic value in jgit.

It was introduced with this change:
git/git@6dbf4b8

I found the relevant references on this discussion

[msohn]

there is a stale change 203182 in review adding support for writing generation numbers

[ifradeo]

That chunk is for GDA2 (generation numbers v2). JGit doesn't support that yet. When the parser finds an unknown chunk, it just logs it and ignores that chunk.

If this bug is about the warning log, we can close it as "working as intended". The actual feature request is "support generation number v2" in jgit.