Re: Assertion in git log graphing [regression in v2.25]

On 1/7/2020 6:48 AM, Jeff King wrote:

On Tue, Jan 07, 2020 at 11:24:50AM +0000, Bradley Smith wrote:

quoted

The following git repository (https://github.com/brads55/git-testcase)
causes an assertion when running:

  $ git log --oneline --graph --all

  git-log: graph.c:1228: graph_output_collapsing_line: Assertion
`graph->mapping[i - 3] == target' failed.

Thanks for the report, and especially for providing a reproduction case!

The problem is new in the v2.25 release candidates, so we should try to
deal with it before the release.

quoted

The assertion seems to be caused by commit
0f0f389f12029b1c3745f8ed7aacfe6b2fc7a6cc. The graph structure of the
above repository is as follows (as produced by v2.24.1):

Yeah, I can confirm that this introduces the problem. I admit to not
following the recent graph changes too closely, so I'll add James to the
cc for attention.

I'm also going to take a look this morning, starting by creating a test.
I reviewed what I could of James' patch series, but I was also unfamiliar
with graph.c and relied on his very substantial test cases to verify the
correctness. Looks like a corner case got missed.

Thanks,
-Stolee