Re: [BUG] A part of an edge from an octopus merge gets colored, even with --color=never

[Noam Postavsky <npostavs@users.sourceforge.net>]

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On Sat, 8 Sep 2018 at 12:13, Jeff King <peff@peff.net> wrote:

> Great (and sorry for the delayed response).

No problem, I know it's not the most urgent bug ever :)

> So I think this is doing the right thing. I'm not sure if there's a
> better way to explain "dashless" or not.

I've updated the comments and renamed a few variables, see if that helps.

> Do you feel comfortable trying to add something to the test suite for
> this?

Um, sort of. I managed to recast my script into the framework of the
other tests (see attached t4299-octopus.sh); it seems like it should
go into t4202-log.sh, but it's not clear to me how I can do this
without breaking all the other tests which expect a certain sequence
of commits.

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From ade526d32f692cae06000bb413ff29dad3f6109e Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@users.sourceforge.net>
Date: Sat, 1 Sep 2018 20:07:16 -0400
Subject: [PATCH v4] log: Fix coloring of certain octupus merge shapes

For octopus merges where the first parent edge immediately merges into
the next column to the left:

| *-.
| |\ \
|/ / /

then the number of columns should be one less than the usual case:

| *-.
| |\ \
| | | *

Also refactor the code to iterate over columns rather than dashes,
building from an initial patch suggestion by Jeff King.

Signed-off-by: Noam Postavsky <npostavs@users.sourceforge.net>
---
 graph.c | 56 +++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 41 insertions(+), 15 deletions(-)

diff --git a/graph.c b/graph.c
index e1f6d3bdd..a3366f6da 100644
--- a/graph.c
+++ b/graph.c
@@ -842,27 +842,53 @@ static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
 }
 
 /*
- * Draw an octopus merge and return the number of characters written.
+ * Draw the horizontal dashes of an octopus merge and return the number of
+ * characters written.
  */
 static int graph_draw_octopus_merge(struct git_graph *graph,
 				    struct strbuf *sb)
 {
 	/*
-	 * Here dashless_commits represents the number of parents
-	 * which don't need to have dashes (because their edges fit
-	 * neatly under the commit).
-	 */
-	const int dashless_commits = 2;
-	int col_num, i;
-	int num_dashes =
-		((graph->num_parents - dashless_commits) * 2) - 1;
-	for (i = 0; i < num_dashes; i++) {
-		col_num = (i / 2) + dashless_commits + graph->commit_index;
-		strbuf_write_column(sb, &graph->new_columns[col_num], '-');
+	 * Here dashless_parents represents the number of parents which don't
+	 * need to have dashes (the edges labeled "0" and "1").  And
+	 * dashful_parents are the remaining ones.
+	 *
+	 * | *---.
+	 * | |\ \ \
+	 * | | | | |
+	 * x 0 1 2 3
+	 *
+	 */
+	const int dashless_parents = 2;
+	int dashful_parents = graph->num_parents - dashless_parents;
+
+	/*
+	 * Usually, each parent gets its own column, like the diagram above, but
+	 * sometimes the first parent goes into an existing column, like this:
+	 *
+	 * | *---.
+	 * | |\ \ \
+	 * |/ / / /
+	 * x 0 1 2
+	 *
+	 * In which case there will be more parents than the delta of columns.
+	 */
+	int delta_cols = (graph->num_new_columns - graph->num_columns);
+	int parent_in_old_cols = graph->num_parents - delta_cols;
+
+	/*
+	 * In both cases, commit_index corresponds to the edge labeled "0".
+	 */
+	int first_col = graph->commit_index + dashless_parents
+	    - parent_in_old_cols;
+
+	int i;
+	for (i = 0; i < dashful_parents; i++) {
+		strbuf_write_column(sb, &graph->new_columns[i+first_col], '-');
+		strbuf_write_column(sb, &graph->new_columns[i+first_col],
+				    i == dashful_parents-1 ? '.' : '-');
 	}
-	col_num = (i / 2) + dashless_commits + graph->commit_index;
-	strbuf_write_column(sb, &graph->new_columns[col_num], '.');
-	return num_dashes + 1;
+	return 2 * dashful_parents;
 }
 
 static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
-- 
2.11.0