Re: git log --merges doesn't show commits as expected

From: Jeff King <peff@peff.net>
Date: Nov 13, 2015, 22:35 UTC
Message-ID: <20151113223523.GB14830@sigill.intra.peff.net>
In-Reply-To: <AMSPR02MB168531F809E1625FACEB25283110@AMSPR02MB168.eurprd02.prod.outlook.com>

On Fri, Nov 13, 2015 at 04:21:36PM +0000, Dominik Rauch wrote:

> (This is my first post to this mailing list and I couldn't find a FAQ
> section - please excuse me, if I haven't followed all the established
> posting guidelines yet.)

This is the right place. Welcome. :)

Show 18 quoted lines

> I have the following repository tree:
> 
> C
> |\
> | B
> | /
> A
> 
> Commit A: Parents=(). Initial commit. Contains file foo with content "ABC".
> Commit B: Parents=(A). Represents a commit on some feature branch. Contains file foo with content "XYZ".
> Commit C: Parents=(A, B). Represents a merge commit of a feature branch back to the main branch. Contains file foo with content "XYZ".
> 
> I expected "git log --merges foo" to show C, however, the log is
> empty! Specifying "--full-history" results in the correct history,
> therefore I assume, I misunderstand Git's default history
> simplification algorithm. Unfortunately, the example in the Git docs
> at [1] does not contain the very same situation (although it is
> probably one of the most common situations...).

I don't think "--merges" is relevant to the simplification here. By asking for "foo", that turns on history simplification. Since the merge at C took one side directly, that means we can cull the parent link that leads to A (its foo=ABC did not contribute to the final outcome). And then C is TREESAME to its only remaining parent (they both have foo=XYZ), so it can be removed, leaving only commit B to be passed to the next stage.

And then we apply "--merges", and see that B is not a merge, and so do not show it (but we still traverse it, of course).

In theory we could apply "--merges" first (by simplifying history to shrink any chains of non-merges to a single point). But I don't think there's any way to do that currently with git.

-Peff