Re: Feature request: add a metadata in the commit: the "commited in branch" information

From: Theodore Y. Ts'o <tytso@mit.edu>
Date: Dec 30, 2019, 04:15 UTC
Message-ID: <20191230041517.GA84036@mit.edu>
In-Reply-To: <CAEW0o+g7vXj841h+4nNK8iSoO758Uh9fLKMCN87RE2w2Nd=CRg@mail.gmail.com>

On Mon, Dec 30, 2019 at 12:53:56AM +0100, Arnaud Bertrand wrote:

Show 13 quoted lines

> Hi Junio,
> 
> It really depends how git is used. With big collaborative project
> (like git or linux kernel), you are totally right.
> for development limited to a company that has developments with team
> of 10-20 developers and that uses
> a correct SCM plan, the name of the branch is regulated and is
> meaningful, mostly  linked to a bug tracking system
> system. For audits and  traceability, the branch name is really
> important... certainly more than the email of the developer ;-)
> So the "contamination" is negligible compare to the bentefit in this context.
> It will also helps the graphical tools to have a comprehensive
> represeintation which can do git even better.

Why does it need to be the branch name? You can add your own extra metadata to the git description. So for example, I might have a git commit that looks like this:

    ext4: avoid declaring fs inconsistent due to invalid file handles

    If we receive a file handle, either from NFS or open_by_handle_at(2),
    and it points at an inode which has not been initialized, and the file
    system has metadata checksums enabled, we shouldn't try to get the
    inode, discover the checksum is invalid, and then declare the file
    system as being inconsistent.

    ... <details of repro omitted to keep this email short>

    Google-Bug-Id: 120690101
    Upstream-5.0-SHA1: 8a363970d1dc38c4ec4ad575c862f776f468d057
    Tested: used the repro to verify that open_by_handle_at(2)
       will not declare the fs inconsistent
    Effort: storage/ext4       
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Change-Id: Iafb6da7c360a4c34b882f7fd6a91e3bb

The tie-in to the bug tracking system is done via "Google-Bug-Id:". The Effort tag is used to identify which subteam should be responsble for rebasing the commit to a newer upstream kernel. (E.g., how to account for all of the patches made on top of 4.14.x when you are rebasing to the newer 4.19 long-term-stable kernel, to make sure all not-yet-usptreamed commits are carried over during the rebase process.)

The Upstream-X.Y-SHA1: tag indicates that this is an upstream commit that was backported to the internal kernel. If the commit isn't an upstream backport, we have a policy (which is enforced via an automated bot when the commit goes through Gerritt for review) that there must be an "Upstream-Plan: " tag indicating how the committer plans to get the change upstream.

The automated review bot also enforces that a Tested: tag exists, describing how the developer tested the change, and Change-Id: is used to link the commit to Gerrit, which is how we enforce that all commits have to be reviewed by a second engineer before it is allowed into the production kernel sources. We also maintain all of the Gerrit comments as history and so we can have accountability as to who reviewed a commit before it was submitted into the release repository.

We also have automated bots which will run checkpatch and note the warnings from checkpatch as Gerrit commits; and if the kernel doesn't build on a variety of architetures and configurations (e.g., debug, installer, etc.) a bot can also report this and add -1 Gerrit review.

See? You can do an awful lot without regulating and recording the branch name used by the engineer. We have full audit and traceability through the Gerrit reviews, and we can use the Google-Bug-Id to track which release versions of which kernels have which bugs fixed.

The bottom line is each company is going to have a different workflow for doing reviews, linkage to bug tracking systems, auditability, etc. If everybody were to demand their unique scheme was to be supported directly in Git, it would be a mess. The scheme that I've described above needs no special git features. It just uses some git hooks as a convenience to to developers to help them fill in these required fields, using Gerrit for commit review, and some bots which submit reviews to Gerrit.

Cheers,

						- Ted