On 10/10/2019 12:13 PM, James Coglan via GitGitGadget wrote:
> From: James Coglan <jcoglan@xxxxxxxxx>
>
> 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@xxxxxxxxx>
> ---
> 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/ *$//" > actual &&
> + test_cmp expect actual
> +'
I should have noticed in your earlier commits, but why don't you keep
the output inside the test suite? You can start with "cat >expect <<-EOF"
to have it ignore leading whitespace. Sorry if there's something else about
this that is causing issues.
> +
> +test_expect_success 'setup nested left-skewed merge following normal merge' '
> + git checkout --orphan 2_p &&
> + test_commit 2_A &&
> + test_commit 2_B &&
> + test_commit 2_C &&
> + git checkout -b 2_q @^^ &&
> + test_commit 2_D &&
> + test_commit 2_E &&
> + git checkout -b 2_r @^ && test_commit 2_F &&
> + git checkout 2_q &&
> + git merge --no-ff 2_r -m 2_G &&
> + git merge --no-ff 2_p^ -m 2_H &&
> + git checkout -b 2_s @^^ && git merge --no-ff 2_q -m 2_J &&
> + git checkout 2_p && git merge --no-ff 2_s -m 2_K
> +'
> +
> +cat > expect <<\EOF
> +* 2_K
> +|\
> +| * 2_J
> +| |\
> +| | * 2_H
> +| | |\
> +| | * | 2_G
> +| |/| |
> +| | * | 2_F
> +| * | | 2_E
> +| |/ /
> +| * | 2_D
> +* | | 2_C
> +| |/
> +|/|
> +* | 2_B
> +|/
> +* 2_A
> +EOF
> +
> +test_expect_success 'log --graph with nested left-skewed merge following normal merge' '
> + git log --graph --pretty=tformat:%s | sed "s/ *$//" > actual &&
> + test_cmp expect actual
> +'
> +
> +test_expect_success 'setup nested right-skewed merge following left-skewed merge' '
> + git checkout --orphan 3_p &&
> + test_commit 3_A &&
> + git checkout -b 3_q &&
> + test_commit 3_B &&
> + test_commit 3_C &&
> + git checkout -b 3_r @^ &&
> + test_commit 3_D &&
> + git checkout 3_q && git merge --no-ff 3_r -m 3_E &&
> + git checkout 3_p && git merge --no-ff 3_q -m 3_F &&
> + git checkout 3_r && test_commit 3_G &&
> + git checkout 3_p && git merge --no-ff 3_r -m 3_H &&
> + git checkout @^^ && git merge --no-ff 3_p -m 3_J
> +'
> +
> +cat > expect <<\EOF
> +* 3_J
> +|\
> +| * 3_H
> +| |\
> +| | * 3_G
> +| * | 3_F
> +|/| |
> +| * | 3_E
> +| |\ \
> +| | |/
> +| | * 3_D
> +| * | 3_C
> +| |/
> +| * 3_B
> +|/
> +* 3_A
> +EOF
> +
> +test_expect_success 'log --graph with nested right-skewed merge following left-skewed merge' '
> + git log --graph --pretty=tformat:%s | sed "s/ *$//" > actual &&
> + test_cmp expect actual
> +'
> +
> +test_expect_success 'setup right-skewed merge following a left-skewed one' '
> + git checkout --orphan 4_p &&
> + test_commit 4_A &&
> + test_commit 4_B &&
> + test_commit 4_C &&
> + git checkout -b 4_q @^^ && test_commit 4_D &&
> + git checkout -b 4_r 4_p^ && git merge --no-ff 4_q -m 4_E &&
> + git checkout -b 4_s 4_p^^ &&
> + git merge --no-ff 4_r -m 4_F &&
> + git merge --no-ff 4_p -m 4_G &&
> + git checkout @^^ && git merge --no-ff 4_s -m 4_H
> +'
> +
> +cat > expect <<\EOF
> +* 4_H
> +|\
> +| * 4_G
> +| |\
> +| * | 4_F
> +|/| |
> +| * | 4_E
> +| |\ \
> +| | * | 4_D
> +| |/ /
> +|/| |
> +| | * 4_C
> +| |/
> +| * 4_B
> +|/
> +* 4_A
> +EOF
> +
> +test_expect_success 'log --graph with right-skewed merge following a left-skewed one' '
> + git log --graph --date-order --pretty=tformat:%s | sed "s/ *$//" > actual &&
> + test_cmp expect actual
> +'
> +
> test_done
>
