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

[Derrick Stolee <stolee@gmail.com>]

On 4/14/2020 4:22 PM, 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.
> 
> 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.

Well, commit-graphs are not supposed to do anything if we have
shallow clones. We definitely don't load a commit-graph in that
case. Seems like we need an extra check in write_commit_graph()
to stop writing in the presence of shallow commits.

-Stolee