Re: Trimming 'deadheads' (TREESAME 2nd parent) from revision walks?

From: Jeff King <peff@peff.net>
Date: Sep 19, 2021, 18:59 UTC
Message-ID: <YUeImAqA0SZAdA2R@coredump.intra.peff.net>
In-Reply-To: <01fe28d8-2887-bc42-c91b-c3237b5186a7@iee.email>

On Sat, Sep 18, 2021 at 03:18:47PM +0100, Philip Oakley wrote:

Show 5 quoted lines

> Is there a method within `git rev-list` to trim side branch merges where
> the merge's tree is identical to the first parent's commit-tree?
> [...]
> From my reading of the `rev-list` manual this is similar to the <paths>
> TREESAME capability, but without specifying any paths (maybe just `.` ?).

Yes, I'd just do "git log ." for this. I don't think there's another way to trigger simplification. In try_to_simplify_commit(), we bail early unless revs->prune is set, and that is set only by the presence of pathspecs or by --simplify-by-decoration.

> * Is there a proper term for the treesame condition of the commit-tree
> (as recorded in the commit object)?

In a one-parent commit, I'd just call it an empty commit. For a merge, it is really I'd probably call it an "ours" merge, since one obvious way to get there is with "git merge -s ours" (of course you can also just resolve all conflicts in favor of one parent). I don't know of another name (besides treesame, of course, but that generally implies a particular scope of interest given by a pathspec).

-Peff