Re: Is fetch.writeCommitGraph (and thus features.experimental) meant to work in the presence of shallow clones?

[Taylor Blau <me@ttaylorr.com>]

On Tue, Apr 14, 2020 at 01:22:45PM -0700, Elijah Newren wrote:
> Hi,
>
> I was building a version of git for internal use, and thought I'd try
> turning on features.experimental to get more testing of it.  The
> following test error in the testsuite scared me, though:
>
> t5537.9 (fetch --update-shallow):
>
> ...
> + git fetch --update-shallow ../shallow/.git refs/heads/*:refs/remotes/shallow/*
> remote: Enumerating objects: 18, done.
> remote: Counting objects: 100% (18/18), done.
> remote: Compressing objects: 100% (6/6), done.
> remote: Total 16 (delta 0), reused 6 (delta 0), pack-reused 0
> Unpacking objects: 100% (16/16), 1.16 KiB | 1.17 MiB/s, done.
> From ../shallow/
>  * [new branch]      master     -> shallow/master
>  * [new tag]         heavy-tag  -> heavy-tag
>  * [new tag]         light-tag  -> light-tag
> error: Could not read ac67d3021b4319951fb176469d7732e6914530c5
> error: Could not read ac67d3021b4319951fb176469d7732e6914530c5
> error: Could not read ac67d3021b4319951fb176469d7732e6914530c5
> fatal: unable to parse commit ac67d3021b4319951fb176469d7732e6914530c5
>
> Passing -c fetch.writeCommitGraph=false to the fetch command in that
> test makes it pass.

This failure makes sense, since taking the reachability closure over
the ref tips will fail in shallow clones of repositories that have more
than one commit.

I wonder if fetch should be taught to avoid generating commit-graphs
(and ignore 'fetch.writeCommitGraph') when in a shallow clone.

> There were also a couple other tests that failed with
> features.experimental=true (in t5500), but those weren't scary -- they
> were just checking exact want/have lines and features.experimental is
> intended to change those.  This test from t5537 was the only one that
> showed some unexpected fatal error.
>
> Thanks,
> Elijah

Thanks,
Taylor