Re: BUG: commit-reach.c:66: bad generation skip

On 2/10/2021 7:18 AM, Filippo Valsorda wrote:

On Mon, Feb 8, 2021 at 3:26 AM Derrick Stolee [off-list ref] wrote:

quoted

_This_ is interesting. I haven't heard of this problem happening
in a released version of Git.

I'm CC'ing Jonathan Nieder who recently saw this happening, but that
was on a newer version than 2.30.0 with a topic that is not part
of 2.30.0. But maybe the version shipped internally is versioned
without extra information on top of the latest tag? (I see your
@google.com email, which makes me think you have an internal version.)

Ah, the issue indeed first showed up as I was using the internal
version. I then installed mainline 2.30.0 to check that it reproduced
on the same local repository before reporting a bug.

The mainline does have the BUG() statement, but it's really reflecting
bad data in the commit-graph file. That data was written by the internal
version and was not reset until you rewrote the file.

quoted

To better understand your situation, could you please run the
following commands?

        git config --get-regexp graph
        git config features.experimental

I'm specifically looking for values of fetch.writeCommitGraph and
gc.writeCommitGraph.

fetch.writecommitgraph is enabled on the internal version.

$ git version
git version 2.30.0.478.g8a0d178c01-goog
$ git config --get-regexp graph
fetch.writecommitgraph true
$ git config features.experimental
$ ~/homebrew/bin/git version
git version 2.30.0
$ ~/homebrew/bin/git config --get-regexp graph
$ ~/homebrew/bin/git config features.experimental

I zipped up the repository and the worktree before running gc, so I can
run other commands for you if you need, but unfortunately I can't share
the archive, as it fetched from a private branch with security fixes.

Thanks, but let me know if it reproduces again. The bug should be fixed
in ds/commit-graph-genno-fix [1], and I think the Google internal release
has been rolled back until that branch is included.

[1] https://github.com/gitster/git/commits/ds/commit-graph-genno-fix

Thanks,
-Stolee