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graph: tidy up display of left-skewed merges 

Currently, when we display a merge whose first parent is already present
in a column to the left of the merge commit, we display the first parent
as a vertical pipe `|` in the GRAPH_POST_MERGE line and then immediately
enter the GRAPH_COLLAPSING state. The first-parent line tracks to the
left and all the other parent lines follow it; this creates a "kink" in
those lines:

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

This change tidies the display of such commits such that if the first
parent appears to the left of the merge, we render it as a `/` and the
second parent as a `|`. This reduces the horizontal and vertical space
needed to render the merge, and makes the resulting lines easier to
read.

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

If the first parent is separated from the merge by several columns, a
horizontal line is drawn in a similar manner to how the GRAPH_COLLAPSING
state displays the line.

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

This effect is applied to both "normal" two-parent merges, and to
octopus merges. It also reduces the vertical space needed for pre-commit
lines, as the merge occupies one less column than usual.

        Before:         After:

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

Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
James Coglan 2019-10-15 23:47:54 +00:00 committed by Junio C Hamano
parent 458152cce1
commit 0f0f389f12
3 changed files with 143 additions and 45 deletions
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123
graph.c
View File

@ -202,6 +202,20 @@ struct git_graph {
* previous commit.
*/
int prev_commit_index;
/*
* Which layout variant to use to display merge commits. If the
* commit's first parent is known to be in a column to the left of the
* merge, then this value is 0 and we use the layout on the left.
* Otherwise, the value is 1 and the layout on the right is used. This
* field tells us how many columns the first parent occupies.
*
* 0) 1)
*
* | | | *-. | | *---.
* | |_|/|\ \ | | |\ \ \
* |/| | | | | | | | | | *
*/
int merge_layout;
/*
* The maximum number of columns that can be stored in the columns
* and new_columns arrays. This is also half the number of entries
@ -313,6 +327,7 @@ struct git_graph *graph_init(struct rev_info *opt)
graph->prev_state = GRAPH_PADDING;
graph->commit_index = 0;
graph->prev_commit_index = 0;
graph->merge_layout = 0;
graph->num_columns = 0;
graph->num_new_columns = 0;
graph->mapping_size = 0;
@ -472,9 +487,11 @@ static int graph_find_new_column_by_commit(struct git_graph *graph,
}

static void graph_insert_into_new_columns(struct git_graph *graph,
struct commit *commit)
struct commit *commit,
int idx)
{
int i = graph_find_new_column_by_commit(graph, commit);
int mapping_idx;

/*
* If the commit is not already in the new_columns array, then add it
@ -486,8 +503,26 @@ static void graph_insert_into_new_columns(struct git_graph *graph,
graph->new_columns[i].color = graph_find_commit_color(graph, commit);
}

graph->mapping[graph->width] = i;
graph->width += 2;
if (graph->num_parents > 1 && idx > -1 && graph->merge_layout == -1) {
/*
* If this is the first parent of a merge, choose a layout for
* the merge line based on whether the parent appears in a
* column to the left of the merge
*/
int dist, shift;

dist = idx - i;
shift = (dist > 1) ? 2 * dist - 3 : 1;

graph->merge_layout = (dist > 0) ? 0 : 1;
mapping_idx = graph->width + (graph->merge_layout - 1) * shift;
graph->width += 2 * graph->merge_layout;
} else {
mapping_idx = graph->width;
graph->width += 2;
}

graph->mapping[mapping_idx] = i;
}

static void graph_update_columns(struct git_graph *graph)
@ -553,6 +588,7 @@ static void graph_update_columns(struct git_graph *graph)
if (col_commit == graph->commit) {
seen_this = 1;
graph->commit_index = i;
graph->merge_layout = -1;
for (parent = first_interesting_parent(graph);
parent;
parent = next_interesting_parent(graph, parent)) {
@ -565,7 +601,7 @@ static void graph_update_columns(struct git_graph *graph)
!is_commit_in_columns) {
graph_increment_column_color(graph);
}
graph_insert_into_new_columns(graph, parent->item);
graph_insert_into_new_columns(graph, parent->item, i);
}
/*
* We always need to increment graph->width by at
@ -576,7 +612,7 @@ static void graph_update_columns(struct git_graph *graph)
if (graph->num_parents == 0)
graph->width += 2;
} else {
graph_insert_into_new_columns(graph, col_commit);
graph_insert_into_new_columns(graph, col_commit, -1);
}
}

@ -588,10 +624,36 @@ static void graph_update_columns(struct git_graph *graph)
graph->mapping_size--;
}

static int graph_num_expansion_rows(struct git_graph *graph)
{
/*
* Normally, we need two expansion rows for each dashed parent line from
* an octopus merge:
*
* | *
* | |\
* | | \
* | | \
* | *-. \
* | |\ \ \
*
* If the merge is skewed to the left, then its parents occupy one less
* column, and we don't need as many expansion rows to route around it;
* in some cases that means we don't need any expansion rows at all:
*
* | *
* | |\
* | * \
* |/|\ \
*/
return (graph->num_parents + graph->merge_layout - 3) * 2;
}

static int graph_needs_pre_commit_line(struct git_graph *graph)
{
return graph->num_parents >= 3 &&
graph->commit_index < (graph->num_columns - 1);
graph->commit_index < (graph->num_columns - 1) &&
graph->expansion_row < graph_num_expansion_rows(graph);
}

void graph_update(struct git_graph *graph, struct commit *commit)
@ -728,7 +790,6 @@ static void graph_output_skip_line(struct git_graph *graph, struct graph_line *l
static void graph_output_pre_commit_line(struct git_graph *graph,
struct graph_line *line)
{
int num_expansion_rows;
int i, seen_this;

/*
@ -739,14 +800,13 @@ static void graph_output_pre_commit_line(struct git_graph *graph,
* We need 2 extra rows for every parent over 2.
*/
assert(graph->num_parents >= 3);
num_expansion_rows = (graph->num_parents - 2) * 2;

/*
* graph->expansion_row tracks the current expansion row we are on.
* It should be in the range [0, num_expansion_rows - 1]
*/
assert(0 <= graph->expansion_row &&
graph->expansion_row < num_expansion_rows);
graph->expansion_row < graph_num_expansion_rows(graph));

/*
* Output the row
@ -786,7 +846,7 @@ static void graph_output_pre_commit_line(struct git_graph *graph,
* and move to state GRAPH_COMMIT if necessary
*/
graph->expansion_row++;
if (graph->expansion_row >= num_expansion_rows)
if (!graph_needs_pre_commit_line(graph))
graph_update_state(graph, GRAPH_COMMIT);
}

@ -824,7 +884,7 @@ static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line
* x 0 1 2 3
*
*/
const int dashless_parents = 2;
const int dashless_parents = 3 - graph->merge_layout;
int dashful_parents = graph->num_parents - dashless_parents;

/*
@ -832,9 +892,9 @@ static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line
* above) but sometimes the first parent goes into an existing column,
* like this:
*
* | *---.
* | |\ \ \
* |/ / / /
* | *-.
* |/|\ \
* | | | |
* x 0 1 2
*
* In which case the number of parents will be one greater than the
@ -925,10 +985,15 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
graph_update_state(graph, GRAPH_COLLAPSING);
}

const char merge_chars[] = {'/', '|', '\\'};

static void graph_output_post_merge_line(struct git_graph *graph, struct graph_line *line)
{
int seen_this = 0;
int i, j;
int i;

struct commit_list *first_parent = first_interesting_parent(graph);
int seen_parent = 0;

/*
* Output the post-merge row
@ -951,30 +1016,34 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
* new_columns and use those to format the
* edges.
*/
struct commit_list *parents = NULL;
struct commit_list *parents = first_parent;
int par_column;
int idx = graph->merge_layout;
char c;
seen_this = 1;
parents = first_interesting_parent(graph);
assert(parents);
par_column = graph_find_new_column_by_commit(graph, parents->item);
assert(par_column >= 0);

graph_line_write_column(line, &graph->new_columns[par_column], '|');
for (j = 0; j < graph->num_parents - 1; j++) {
parents = next_interesting_parent(graph, parents);
assert(parents);
for (; parents; parents = next_interesting_parent(graph, parents)) {
par_column = graph_find_new_column_by_commit(graph, parents->item);
assert(par_column >= 0);
graph_line_write_column(line, &graph->new_columns[par_column], '\\');
graph_line_addch(line, ' ');

c = merge_chars[idx];
graph_line_write_column(line, &graph->new_columns[par_column], c);
if (idx == 2)
graph_line_addch(line, ' ');
else
idx++;
}
} else if (seen_this) {
graph_line_write_column(line, col, '\\');
graph_line_addch(line, ' ');
} else {
graph_line_write_column(line, col, '|');
graph_line_addch(line, ' ');
if (graph->merge_layout != 0 || i != graph->commit_index - 1)
graph_line_addch(line, seen_parent ? '_' : ' ');
}

if (col_commit == first_parent->item)
seen_parent = 1;
}

/*

20
t/t4214-log-graph-octopus.sh
View File

@ -26,9 +26,8 @@ test_expect_success 'set up merge history' '
test_expect_success 'log --graph with tricky octopus merge, no color' '
cat >expect.uncolored <<-\EOF &&
* left
| *---. octopus-merge
| |\ \ \
|/ / / /
| *-. octopus-merge
|/|\ \
| | | * 4
| | * | 3
| | |/
@ -47,9 +46,8 @@ test_expect_success 'log --graph with tricky octopus merge with colors' '
test_config log.graphColors red,green,yellow,blue,magenta,cyan &&
cat >expect.colors <<-\EOF &&
* left
<RED>|<RESET> *<BLUE>-<RESET><BLUE>-<RESET><MAGENTA>-<RESET><MAGENTA>.<RESET> octopus-merge
<RED>|<RESET> <RED>|<RESET><YELLOW>\<RESET> <BLUE>\<RESET> <MAGENTA>\<RESET>
<RED>|<RESET><RED>/<RESET> <YELLOW>/<RESET> <BLUE>/<RESET> <MAGENTA>/<RESET>
<RED>|<RESET> *<MAGENTA>-<RESET><MAGENTA>.<RESET> octopus-merge
<RED>|<RESET><RED>/<RESET><YELLOW>|<RESET><BLUE>\<RESET> <MAGENTA>\<RESET>
<RED>|<RESET> <YELLOW>|<RESET> <BLUE>|<RESET> * 4
<RED>|<RESET> <YELLOW>|<RESET> * <MAGENTA>|<RESET> 3
<RED>|<RESET> <YELLOW>|<RESET> <MAGENTA>|<RESET><MAGENTA>/<RESET>
@ -147,9 +145,8 @@ test_expect_success 'log --graph with tricky octopus merge and its child, no col
cat >expect.uncolored <<-\EOF &&
* left
| * after-merge
| *---. octopus-merge
| |\ \ \
|/ / / /
| *-. octopus-merge
|/|\ \
| | | * 4
| | * | 3
| | |/
@ -169,9 +166,8 @@ test_expect_failure 'log --graph with tricky octopus merge and its child with co
cat >expect.colors <<-\EOF &&
* left
<RED>|<RESET> * after-merge
<RED>|<RESET> *<MAGENTA>-<RESET><MAGENTA>-<RESET><CYAN>-<RESET><CYAN>.<RESET> octopus-merge
<RED>|<RESET> <RED>|<RESET><BLUE>\<RESET> <MAGENTA>\<RESET> <CYAN>\<RESET>
<RED>|<RESET><RED>/<RESET> <BLUE>/<RESET> <MAGENTA>/<RESET> <CYAN>/<RESET>
<RED>|<RESET> *<CYAN>-<RESET><CYAN>.<RESET> octopus-merge
<RED>|<RESET><RED>/<RESET><BLUE>|<RESET><MAGENTA>\<RESET> <CYAN>\<RESET>
<RED>|<RESET> <BLUE>|<RESET> <MAGENTA>|<RESET> * 4
<RED>|<RESET> <BLUE>|<RESET> * <CYAN>|<RESET> 3
<RED>|<RESET> <BLUE>|<RESET> <CYAN>|<RESET><CYAN>/<RESET>

45
t/t4215-log-skewed-merges.sh
View File

@ -11,12 +11,8 @@ test_expect_success 'log --graph with merge fusing with its left and right neigh
| * G
| |\
| | * F
| | |
| | \
| *-. \ E
| |\ \ \
|/ / / /
| | | /
| * \ E
|/|\ \
| | |/
| | * D
| * | C
@ -40,4 +36,41 @@ test_expect_success 'log --graph with merge fusing with its left and right neigh
test_cmp expect actual
'

test_expect_success 'log --graph with left-skewed merge' '
cat >expect <<-\EOF &&
*-----. 0_H
|\ \ \ \
| | | | * 0_G
| |_|_|/|
|/| | | |
| | | * \ 0_F
| |_|/|\ \
|/| | | |/
| | | | * 0_E
| |_|_|/
|/| | |
| | * | 0_D
| | |/
| | * 0_C
| |/
|/|
| * 0_B
|/
* 0_A
EOF

git checkout --orphan 0_p && test_commit 0_A &&
git checkout -b 0_q 0_p && test_commit 0_B &&
git checkout -b 0_r 0_p &&
test_commit 0_C &&
test_commit 0_D &&
git checkout -b 0_s 0_p && test_commit 0_E &&
git checkout -b 0_t 0_p && git merge --no-ff 0_r^ 0_s -m 0_F &&
git checkout 0_p && git merge --no-ff 0_s -m 0_G &&
git checkout @^ && git merge --no-ff 0_q 0_r 0_t 0_p -m 0_H &&

git log --graph --pretty=tformat:%s | sed "s/ *$//" >actual &&
test_cmp expect actual
'

test_done