Re: [BUG/PATCH 0/5] t4214: cleanup and demonstrate graph bug

From: Denton Liu <liu.denton@gmail.com>
Date: Sep 25, 2019, 17:09 UTC
Message-ID: <20190925170902.GA11547@dentonliu-ltm.internal.salesforce.com>
In-Reply-To: <cover.1569407150.git.liu.denton@gmail.com>

On Wed, Sep 25, 2019 at 03:26:57AM -0700, Denton Liu wrote:

> I tried my hand at fixing the bug but in the hour I spent going at it, I
> couldn't fix the logic up. The buggy logic is in graph.c:
> graph_draw_octopus_merge() in case anyone is interested.

I guess for the record, this was the final patch that I ended up with. Two issues with it, though:

1. It assumes that there can be no parallel paths on the right side,
which I'm not sure is a correct assumption.

2. It _still_ fails my last proposed test case.

-- >8 --

diff --git a/graph.c b/graph.c
index f53135485f..f9395a2327 100644
--- a/graph.c
+++ b/graph.c
@@ -881,8 +881,7 @@ static int graph_draw_octopus_merge(struct git_graph *graph,
 	/*
 	 * In both cases, commit_index corresponds to the edge labeled "0".
 	 */
-	int first_col = graph->commit_index + dashless_parents
-	    - parent_in_old_cols;
+	int first_col = graph->num_new_columns - dashful_parents;
 
 	int i;
 	for (i = 0; i < dashful_parents; i++) {