Re: Link trailers revisited (was Re: [GIT PULL] io_uring fix for 6.17-rc5)

[<dan.j.williams@intel.com>]

Konstantin Ryabitsev wrote:
> On Tue, Sep 09, 2025 at 10:58:53AM -0700, Linus Torvalds wrote:
> > On Tue, 9 Sept 2025 at 10:50, Linus Torvalds
> > <torvalds@linux-foundation.org> wrote:
> > >
> > >    patchid=$(git diff-tree -p fef7ded169ed7e133612f90a032dc2af1ce19bef
> > > | git patch-id | cut -d' ' -f1)
> > 
> > Oh, and looking more at that, use Dan's version instead.  You almost
> > certainly want to use '--stable' like Dan did, although maybe
> > Konstantin can speak up on what option lore actually uses for
> > indexing.
> 
> It uses --stable.
> 
> > And you *can* screw up patchid matching. In particular, you can
> > generate patches different ways, and patch-id won't generate the same
> > thing for a rename patch and a add/delete patch, for example (again:
> > the traditional use case is that you generate the patch IDs all from
> > the same tree, so you control how you generate the patches)
> 
> We can't control how the patches are generated by submitters. If someone
> generates and sends them with --histogram, this won't work. Here's an example
> right from your tree:
> 
>     $ git show 1c67f9c54cdc70627e3f6472b89cd3d895df974c | git patch-id --stable | cut -d' ' -f1
>     57cb8d951fd1006d885f6bc7083283d3bc6040c1
> 
>     $ git show --histogram 1c67f9c54cdc70627e3f6472b89cd3d895df974c | git patch-id --stable | cut -d' ' -f1
>     47b4bfff33d1456d0a2bb30f8bd74e1cfe9eb31e
> 
> Or if someone generates with -U5 instead of the default (-U3):
> 
>     $ git show 1c67f9c54cdc70627e3f6472b89cd3d895df974c -U5 | git patch-id --stable | cut -d' ' -f1
>     0b68dd472dc791447c3091f7a671e7f1e5d7a3d2

Is this a matter of teach git send-email to generate a header, e.g.
"X-Patch-ID:", for a given stable diff format convention? That lets
submitters use any diff format they want, but the X-Patch-ID: is
constant. Then "git show $diff_opts_convention $commit" becomes more
reliable over time.

It still does not help the problem of maintainers massaging patches on
their way upstream, but patch.msgid.link does not help that either
because that Link: is not the patch that was merged. So if you care
about automated tooling being able to query lore for commits, the
maintainer simply needs to push modified patches back out to the list,
or accept the consequences of disconnecting the commit from the lore
lookups.