Re: [RFC PATCH 0/1] commit-graph.c: handle corrupt commit trees

From: Garima Singh <garimasigit@gmail.com>
Date: Sep 4, 2019, 18:25 UTC
Message-ID: <c5ba4eaa-f995-5f2e-4f0f-a8f59ba65fd3@gmail.com>
In-Reply-To: <cover.1567563244.git.me@ttaylorr.com>

On 9/3/2019 10:22 PM, Taylor Blau wrote:

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> Hi,
> 
> I was running some of the new 'git commit-graph' commands, and noticed
> that I could consistently get 'git commit-graph write --reachable' to
> segfault when a commit's root tree is corrupt.
> 
> I have an extremely-unfinished fix attached as an RFC PATCH below, but I
> wanted to get a few thoughts on this before sending it out as a non-RFC.
> 
> In my patch, I simply 'die()' when a commit isn't able to be parsed
> (i.e., when 'parse_commit_no_graph' returns a non-zero code), but I
> wanted to see if others thought that this was an OK approach. Some
> thoughts:

I like the idea of completely bailing if the commit can't be parsed too. Only question: Is there a reason you chose to die() instead of BUG() like the other two places in that function? What is the criteria of choosing one over the other?

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> 
>    * It seems like we could write a commit-graph by placing a "filler"
>      entry where the broken commit would have gone. I don't see any place
>      where this is implemented currently, but this seems like a viable
>      alternative to not writing _any_ commits into the commit-graph.

I would rather we didn't do this cause it will probably kick open the can of always watching for that filler when we are working with the commit-graph. Or do we already do that today? Maybe @stolee can chime in on what we do in cases of shallow clones and other potential gaps in the walk

-Garima