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> On 10/10/2019 12:13 PM, James Coglan via GitGitGadget wrote:
>> From: James Coglan <jcoglan@gmail.com>
>>
>> Following the introduction of "left-skewed" merges, which are merges
>> whose first parent fuses with another edge to its left, we have some
>> more edge cases to deal with in the display of commit and post-merge
>> lines.
>>
>> The current graph code handles the following cases for edges appearing
>> to the right of the commit (*) on commit lines. A 2-way merge is usually
>> followed by vertical lines:
>>
>> | | |
>> | * |
>> | |\ \
>>
>> An octopus merge (more than two parents) is always followed by edges
>> sloping to the right:
>>
>> | | \ | | \
>> | *-. \ | *---. \
>> | |\ \ \ | |\ \ \ \
>>
>> A 2-way merge is followed by a right-sloping edge if the commit line
>> immediately follows a post-merge line for a commit that appears in the
>> same column as the current commit, or any column to the left of that:
>>
>> | * | * |
>> | |\ | |\ \
>> | * \ | | * \
>> | |\ \ | | |\ \
>>
>> This commit introduces the following new cases for commit lines. If a
>> 2-way merge skews to the left, then the edges to its right are always
>> vertical lines, even if the commit follows a post-merge line:
>>
>> | | | | |\
>> | * | | * |
>> |/| | |/| |
>>
>> A commit with 3 parents that skews left is followed by vertical edges:
>>
>> | | |
>> | * |
>> |/|\ \
>>
>> If a 3-way left-skewed merge commit appears immediately after a
>> post-merge line, then it may be followed the right-sloping edges, just
>> like a 2-way merge that is not skewed.
>>
>> | |\
>> | * \
>> |/|\ \
>>
>> Octopus merges with 4 or more parents that skew to the left will always
>> be followed by right-sloping edges, because the existing columns need to
>> expand around the merge.
>>
>> | | \
>> | *-. \
>> |/|\ \ \
>>
>> On post-merge lines, usually all edges following the current commit
>> slope to the right:
>>
>> | * | |
>> | |\ \ \
>>
>> However, if the commit is a left-skewed 2-way merge, the edges to its
>> right remain vertical. We also need to display a space after the
>> vertical line descending from the commit marker, whereas this line would
>> normally be followed by a backslash.
>>
>> | * | |
>> |/| | |
>>
>> If a left-skewed merge has more than 2 parents, then the edges to its
>> right are still sloped as they bend around the edges introduced by the
>> merge.
>>
>> | * | |
>> |/|\ \ \
>>
>> To handle these new cases, we need to know not just how many parents
>> each commit has, but how many new columns it adds to the display; this
>> quantity is recorded in the `edges_added` field for the current commit,
>> and `prev_edges_added` field for the previous commit.
>>
>> Here, "column" refers to visual columns, not the logical columns of the
>> `columns` array. This is because even if all the commit's parents end up
>> fusing with existing edges, they initially introduce distinct edges in
>> the commit and post-merge lines before those edges collapse. For
>> example, a 3-way merge whose 2nd and 3rd parents fuse with existing
>> edges still introduces 2 visual columns that affect the display of edges
>> to their right.
>>
>> | | | \
>> | | *-. \
>> | | |\ \ \
>> | |_|/ / /
>> |/| | / /
>> | | |/ /
>> | |/| |
>> | | | |
>>
>> This merge does not introduce any *logical* columns; there are 4 edges
>> before and after this commit once all edges have collapsed. But it does
>> initially introduce 2 new edges that need to be accommodated by the
>> edges to their right.
>>
>> Signed-off-by: James Coglan <jcoglan@gmail.com>
>> ---
>> graph.c | 63 +++++++++++++--
>> t/t4215-log-skewed-merges.sh | 151 +++++++++++++++++++++++++++++++++++
>> 2 files changed, 209 insertions(+), 5 deletions(-)
>>
>> diff --git a/graph.c b/graph.c
>> index 9136173e03..fb2e42850f 100644
>> --- a/graph.c
>> +++ b/graph.c
>> @@ -197,6 +197,46 @@ struct git_graph {
>> * |/| | | | | | | | | | *
>> */
>> int merge_layout;
>> + /*
>> + * The number of columns added to the graph by the current commit. For
>> + * 2-way and octopus merges, this is is usually one less than the
>> + * number of parents:
>> + *
>> + * | | | | | \
>> + * | * | | *---. \
>> + * | |\ \ | |\ \ \ \
>> + * | | | | | | | | | |
>> + *
>> + * num_parents: 2 num_parents: 4
>> + * edges_added: 1 edges_added: 3
>> + *
>> + * For left-skewed merges, the first parent fuses with its neighbor and
>> + * so one less column is added:
>> + *
>> + * | | | | | \
>> + * | * | | *-. \
>> + * |/| | |/|\ \ \
>> + * | | | | | | | |
>> + *
>> + * num_parents: 2 num_parents: 4
>> + * edges_added: 0 edges_added: 2
>> + *
>> + * This number determines how edges to the right of the merge are
>> + * displayed in commit and post-merge lines; if no columns have been
>> + * added then a vertical line should be used where a right-tracking
>> + * line would otherwise be used.
>> + *
>> + * | * \ | * |
>> + * | |\ \ |/| |
>> + * | | * \ | * |
>> + */
>> + int edges_added;
>> + /*
>> + * The number of columns added by the previous commit, which is used to
>> + * smooth edges appearing to the right of a commit in a commit line
>> + * following a post-merge line.
>> + */
>> + int prev_edges_added;
>> /*
>> * The maximum number of columns that can be stored in the columns
>> * and new_columns arrays. This is also half the number of entries
>> @@ -309,6 +349,8 @@ struct git_graph *graph_init(struct rev_info *opt)
>> graph->commit_index = 0;
>> graph->prev_commit_index = 0;
>> graph->merge_layout = 0;
>> + graph->edges_added = 0;
>> + graph->prev_edges_added = 0;
>> graph->num_columns = 0;
>> graph->num_new_columns = 0;
>> graph->mapping_size = 0;
>> @@ -670,6 +712,9 @@ void graph_update(struct git_graph *graph, struct commit *commit)
>> */
>> graph_update_columns(graph);
>>
>> + graph->prev_edges_added = graph->edges_added;
>> + graph->edges_added = graph->num_parents + graph->merge_layout - 2;
>> +
>> graph->expansion_row = 0;
>>
>> /*
>> @@ -943,12 +988,13 @@ static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
>>
>> if (graph->num_parents > 2)
>> graph_draw_octopus_merge(graph, sb);
>> - } else if (seen_this && (graph->num_parents > 2)) {
>> + } else if (seen_this && (graph->edges_added > 1)) {
>> strbuf_write_column(sb, col, '\\');
>> - } else if (seen_this && (graph->num_parents == 2)) {
>> + } else if (seen_this && (graph->edges_added == 1)) {
>> /*
>> - * This is a 2-way merge commit.
>> - * There is no GRAPH_PRE_COMMIT stage for 2-way
>> + * This is either a right-skewed 2-way merge
>> + * commit, or a left-skewed 3-way merge.
>> + * There is no GRAPH_PRE_COMMIT stage for such
>> * merges, so this is the first line of output
>> * for this commit. Check to see what the previous
>> * line of output was.
>> @@ -960,6 +1006,7 @@ static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
>> * makes the output look nicer.
>> */
>> if (graph->prev_state == GRAPH_POST_MERGE &&
>> + graph->prev_edges_added > 0 &&
>> graph->prev_commit_index < i)
>> strbuf_write_column(sb, col, '\\');
>> else
>> @@ -1031,8 +1078,14 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf
>> else
>> idx++;
>> }
>> + if (graph->edges_added == 0)
>> + strbuf_addch(sb, ' ');
>> +
>> } else if (seen_this) {
>> - strbuf_write_column(sb, col, '\\');
>> + if (graph->edges_added > 0)
>> + strbuf_write_column(sb, col, '\\');
>> + else
>> + strbuf_write_column(sb, col, '|');
>> strbuf_addch(sb, ' ');
>> } else {
>> strbuf_write_column(sb, col, '|');
>> diff --git a/t/t4215-log-skewed-merges.sh b/t/t4215-log-skewed-merges.sh
>> index cfaba40f97..e479d6e676 100755
>> --- a/t/t4215-log-skewed-merges.sh
>> +++ b/t/t4215-log-skewed-merges.sh
>> @@ -39,4 +39,155 @@ test_expect_success 'log --graph with left-skewed merge' '
>> test_cmp expect actual
>> '
>>
>> +test_expect_success 'setup nested left-skewed merge' '
>> + git checkout --orphan 1_p &&
>> + test_commit 1_A &&
>> + test_commit 1_B &&
>> + test_commit 1_C &&
>> + git checkout -b 1_q @^ && test_commit 1_D &&
>> + git checkout 1_p && git merge --no-ff 1_q -m 1_E &&
>> + git checkout -b 1_r @~3 && test_commit 1_F &&
>> + git checkout 1_p && git merge --no-ff 1_r -m 1_G &&
>> + git checkout @^^ && git merge --no-ff 1_p -m 1_H
>> +'
>> +
>> +cat > expect <<\EOF
>> +* 1_H
>> +|\
>> +| * 1_G
>> +| |\
>> +| | * 1_F
>> +| * | 1_E
>> +|/| |
>> +| * | 1_D
>> +* | | 1_C
>> +|/ /
>> +* | 1_B
>> +|/
>> +* 1_A
>> +EOF
>> +
>> +test_expect_success 'log --graph with nested left-skewed merge' '
>> + git log --graph --pretty=tformat:%s | sed "s/ *$//" > actual &&
>> + test_cmp expect actual
>> +'
>
> I should have noticed in your earlier commits, but why don't you keep
> the output inside the test suite? You can start with "cat >expect <<-EOF"
> to have it ignore leading whitespace. Sorry if there's something else about
> this that is causing issues.James Coglan <jcoglan@gmail.com>