Re: [PATCH] t4202 (log): add failing test for log with subtree

From: Ramkumar Ramachandra <artagnon@gmail.com>
Date: Apr 22, 2013, 15:46 UTC
Message-ID: <CALkWK0kgQqhG_ojuxZ85mTF8rhLf=wv5dGamU8z+cFxpN7QWYQ@mail.gmail.com>
In-Reply-To: <87wqruk2pj.fsf@linux-k42r.v.cablecom.net>

Thomas Rast wrote:

Show 9 quoted lines

> So (I think?) in the above you claim that $USER interprets
>
>   git log -- README.md
>
> as
>
>   Show me the history of README.md.
>
> But there's no such thing as the history of a file!

I made no such claims. I might not know as much as you or the others on the list about git, but I can certainly grok how git stores history.

There needs to be some amount of mutual respect for a healthy conversation: if you start assuming midway that I don't understand what history is, we have a problem.

> So please don't write tests that go contrary to that definition, because
> they're *wrong*.  The current implementation precisely matches the
> current definition of pathspec filtering.

Who said anything about changing any definitions? Where are you getting all this from?

How does "git log HEAD~3 -- README" work? It sets up a revision walk to start from HEAD~3 going all the way down to the root commit. In each of these commits, it looks for the entry "README" in the corresponding tree. It then runs diff-tree with the previous commit's tree to see if the object (blob) corresponding to the "README" entry is different: if so, it selects the commit and displays it.

Now, what am I saying? I'm saying that this approach assumes that all trees are read into /. A pathspec "subproject/README" is _only_ present in the subtree-merge commit^{tree} and nowhere else. The current log algorithm might try to look for the entry "subproject/README" (your pathspec) in all the commit^{tree}s of the commits leading up to M^2. That is _not_ the problem, as I have already illustrated that --follow follows over merges. The problem is looking for the pathspec "subproject/README" in the first place: those commit^{trees}s have the entry stored as "README".

Am I making any sense, or are you going to accuse me of not understanding trees now?