From b2faaaec1193c64f7366e26a569ca6e231cbd478 Mon Sep 17 00:00:00 2001
From: Pablo Sabater <pabloosabaterr@gmail.com>
Date: Sat, 28 Mar 2026 01:11:11 +0100
Subject: [PATCH 1/3] graph: limit the graph width to a hard-coded max

Repositories that have many active branches at the same time
produce wide graphs. A lane consists of two columns, the edge and the
padding (or another edge), each branch takes a lane in the graph and
there is no way to limit how many can be shown.

Limit the graph engine to draw at most 15 lanes. Lanes over the limit are
not rendered.

On the commit line, if the commit lives on a visible lane, show the
normal commit mark and stop rendering. If the commit lives on the
first hidden lane, show the "*" commit mark so it is known that
this commit lives in the first hidden lane. Commits on deeper lanes
aren't rendered, but the commit subject will always remain.

For merges, the post-merge lane is only needed when the commit or
the first parent lives on a visible lane (to draw the connection
between them), when both are on hidden lanes, post-merge carries
no useful information, skip it and go to collapsing or padding state.

Also fix a pre-existing indentation issue.

The hard-coded limit will be replaced by a user-facing option
on a subsequent commit.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 graph.c | 161 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 136 insertions(+), 25 deletions(-)

diff --git a/graph.c b/graph.c
index 26f6fbf000..70458cf323 100644
--- a/graph.c
+++ b/graph.c
@@ -82,6 +82,8 @@ static void graph_show_line_prefix(const struct diff_options *diffopt)
 static const char **column_colors;
 static unsigned short column_colors_max;
 
+static unsigned int max_lanes = 15;
+
 static void parse_graph_colors_config(struct strvec *colors, const char *string)
 {
 	const char *end, *start;
@@ -317,6 +319,11 @@ struct git_graph {
 	struct strbuf prefix_buf;
 };
 
+static inline int graph_needs_truncation(int lane)
+{
+	return lane >= max_lanes;
+}
+
 static const char *diff_output_prefix_callback(struct diff_options *opt, void *data)
 {
 	struct git_graph *graph = data;
@@ -607,7 +614,7 @@ static void graph_update_columns(struct git_graph *graph)
 {
 	struct commit_list *parent;
 	int max_new_columns;
-	int i, seen_this, is_commit_in_columns;
+	int i, seen_this, is_commit_in_columns, max;
 
 	/*
 	 * Swap graph->columns with graph->new_columns
@@ -696,6 +703,14 @@ static void graph_update_columns(struct git_graph *graph)
 		}
 	}
 
+	/*
+	 * Cap to the hard-coded limit.
+	 * Allow commits from merges to align to the merged lane.
+	 */
+	max = max_lanes * 2 + 2;
+	if (graph->width > max)
+		graph->width = max;
+
 	/*
 	 * Shrink mapping_size to be the minimum necessary
 	 */
@@ -846,6 +861,8 @@ static void graph_output_padding_line(struct git_graph *graph,
 	 * Output a padding row, that leaves all branch lines unchanged
 	 */
 	for (i = 0; i < graph->num_new_columns; i++) {
+		if (graph_needs_truncation(i))
+			break;
 		graph_line_write_column(line, &graph->new_columns[i], '|');
 		graph_line_addch(line, ' ');
 	}
@@ -903,6 +920,8 @@ static void graph_output_pre_commit_line(struct git_graph *graph,
 			seen_this = 1;
 			graph_line_write_column(line, col, '|');
 			graph_line_addchars(line, ' ', graph->expansion_row);
+		} else if (seen_this && graph_needs_truncation(i)) {
+			break;
 		} else if (seen_this && (graph->expansion_row == 0)) {
 			/*
 			 * This is the first line of the pre-commit output.
@@ -994,6 +1013,14 @@ static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line
 		col = &graph->new_columns[j];
 
 		graph_line_write_column(line, col, '-');
+
+		/*
+		 * Commit is at commit_index, each iteration move one lane to
+		 * the right from the commit.
+		 */
+		if (graph_needs_truncation(graph->commit_index + 1 + i))
+			break;
+
 		graph_line_write_column(line, col, (i == dashed_parents - 1) ? '.' : '-');
 	}
 
@@ -1028,8 +1055,16 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 			seen_this = 1;
 			graph_output_commit_char(graph, line);
 
+			if (graph_needs_truncation(i)) {
+				graph_line_addch(line, ' ');
+				break;
+			}
+
 			if (graph->num_parents > 2)
 				graph_draw_octopus_merge(graph, line);
+		} else if (graph_needs_truncation(i)) {
+			seen_this = 1;
+			break;
 		} else if (seen_this && (graph->edges_added > 1)) {
 			graph_line_write_column(line, col, '\\');
 		} else if (seen_this && (graph->edges_added == 1)) {
@@ -1065,13 +1100,46 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 
 	/*
 	 * Update graph->state
+	 *
+	 * If the commit is a merge and the first parent is in a visible lane,
+	 * then the GRAPH_POST_MERGE is needed to draw the merge lane.
+	 *
+	 * If the commit is over the truncation limit, but the first parent is on
+	 * a visible lane, then we still need the merge lane but truncated.
+	 *
+	 * If both commit and first parent are over the truncation limit, then
+	 * there's no need to draw the merge lane because it would work as a
+	 * padding lane.
 	 */
-	if (graph->num_parents > 1)
-		graph_update_state(graph, GRAPH_POST_MERGE);
-	else if (graph_is_mapping_correct(graph))
+	if (graph->num_parents > 1) {
+		if (!graph_needs_truncation(graph->commit_index)) {
+			graph_update_state(graph, GRAPH_POST_MERGE);
+		} else {
+			struct commit_list *p = first_interesting_parent(graph);
+			int lane;
+
+			/*
+			 * graph->num_parents are found using first_interesting_parent
+			 * and next_interesting_parent so it can't be a scenario
+			 * where num_parents > 1 and there are no interesting parents
+			 */
+			if (!p)
+				BUG("num_parents > 1 but no interesting parent");
+
+			lane = graph_find_new_column_by_commit(graph, p->item);
+
+			if (!graph_needs_truncation(lane))
+				graph_update_state(graph, GRAPH_POST_MERGE);
+			else if (graph_is_mapping_correct(graph))
+				graph_update_state(graph, GRAPH_PADDING);
+			else
+				graph_update_state(graph, GRAPH_COLLAPSING);
+		}
+	} else if (graph_is_mapping_correct(graph)) {
 		graph_update_state(graph, GRAPH_PADDING);
-	else
+	} else {
 		graph_update_state(graph, GRAPH_COLLAPSING);
+	}
 }
 
 static const char merge_chars[] = {'/', '|', '\\'};
@@ -1109,6 +1177,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 			int par_column;
 			int idx = graph->merge_layout;
 			char c;
+			int truncated = 0;
 			seen_this = 1;
 
 			for (j = 0; j < graph->num_parents; j++) {
@@ -1117,23 +1186,53 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 
 				c = merge_chars[idx];
 				graph_line_write_column(line, &graph->new_columns[par_column], c);
+
+				/*
+				 * j counts parents, it needs to be halved to be
+				 * comparable with i. Don't truncate if there are
+				 * no more lanes to print (end of the lane)
+				 */
+				if (graph_needs_truncation(j / 2 + i) &&
+				    j / 2 + i <= graph->num_columns) {
+					if ((j + i * 2) % 2 != 0)
+						graph_line_addch(line, ' ');
+					truncated = 1;
+					break;
+				}
+
 				if (idx == 2) {
-					if (graph->edges_added > 0 || j < graph->num_parents - 1)
+					/*
+					 * Check if the next lane needs truncation
+					 * to avoid having the padding doubled
+					 */
+					if (graph_needs_truncation((j + 1) / 2 + i) &&
+					    j < graph->num_parents - 1) {
+						truncated = 1;
+						break;
+					} else if (graph->edges_added > 0 || j < graph->num_parents - 1)
 						graph_line_addch(line, ' ');
 				} else {
 					idx++;
 				}
 				parents = next_interesting_parent(graph, parents);
 			}
+			if (truncated)
+				break;
 			if (graph->edges_added == 0)
 				graph_line_addch(line, ' ');
-
+		} else if (graph_needs_truncation(i)) {
+			break;
 		} else if (seen_this) {
 			if (graph->edges_added > 0)
 				graph_line_write_column(line, col, '\\');
 			else
 				graph_line_write_column(line, col, '|');
-			graph_line_addch(line, ' ');
+			/*
+			 * If it's between two lanes and next would be truncated,
+			 * don't add space padding.
+			 */
+			if (!graph_needs_truncation(i + 1))
+				graph_line_addch(line, ' ');
 		} else {
 			graph_line_write_column(line, col, '|');
 			if (graph->merge_layout != 0 || i != graph->commit_index - 1) {
@@ -1164,6 +1263,7 @@ static void graph_output_collapsing_line(struct git_graph *graph, struct graph_l
 	short used_horizontal = 0;
 	int horizontal_edge = -1;
 	int horizontal_edge_target = -1;
+	int truncated = 0;
 
 	/*
 	 * Swap the mapping and old_mapping arrays
@@ -1279,26 +1379,34 @@ static void graph_output_collapsing_line(struct git_graph *graph, struct graph_l
 	 */
 	for (i = 0; i < graph->mapping_size; i++) {
 		int target = graph->mapping[i];
-		if (target < 0)
-			graph_line_addch(line, ' ');
-		else if (target * 2 == i)
-			graph_line_write_column(line, &graph->new_columns[target], '|');
-		else if (target == horizontal_edge_target &&
-			 i != horizontal_edge - 1) {
-				/*
-				 * Set the mappings for all but the
-				 * first segment to -1 so that they
-				 * won't continue into the next line.
-				 */
-				if (i != (target * 2)+3)
-					graph->mapping[i] = -1;
-				used_horizontal = 1;
-			graph_line_write_column(line, &graph->new_columns[target], '_');
+
+		if (!truncated && graph_needs_truncation(i / 2)) {
+			truncated = 1;
+		}
+
+		if (target < 0) {
+			if (!truncated)
+				graph_line_addch(line, ' ');
+		} else if (target * 2 == i) {
+			if (!truncated)
+				graph_line_write_column(line, &graph->new_columns[target], '|');
+		} else if (target == horizontal_edge_target &&
+			   i != horizontal_edge - 1) {
+			/*
+			 * Set the mappings for all but the
+			 * first segment to -1 so that they
+			 * won't continue into the next line.
+			 */
+			if (i != (target * 2)+3)
+				graph->mapping[i] = -1;
+			used_horizontal = 1;
+			if (!truncated)
+				graph_line_write_column(line, &graph->new_columns[target], '_');
 		} else {
 			if (used_horizontal && i < horizontal_edge)
 				graph->mapping[i] = -1;
-			graph_line_write_column(line, &graph->new_columns[target], '/');
-
+			if (!truncated)
+				graph_line_write_column(line, &graph->new_columns[target], '/');
 		}
 	}
 
@@ -1372,6 +1480,9 @@ static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
 	for (i = 0; i < graph->num_columns; i++) {
 		struct column *col = &graph->columns[i];
 
+		if (graph_needs_truncation(i))
+			break;
+
 		graph_line_write_column(&line, col, '|');
 
 		if (col->commit == graph->commit && graph->num_parents > 2) {

From f756a3c78d4d88af1701996394650e6df6f66170 Mon Sep 17 00:00:00 2001
From: Pablo Sabater <pabloosabaterr@gmail.com>
Date: Sat, 28 Mar 2026 01:11:12 +0100
Subject: [PATCH 2/3] graph: add --graph-lane-limit option

Replace the hard-coded lane limit with a user-facing
option '--graph-lane-limit=<n>'. It caps the number of
visible lanes to n. This option requires '--graph', without
it, limiting the graph has no meaning, in this case error out.

Zero and negative values are valid inputs but silently
ignored treating them as "no limit", the same as not using
the option. This follows what '--max-parents' does with
negative values.

The default is 0, same as not being used.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/rev-list-options.adoc |   5 +
 graph.c                             |  53 +++++-----
 revision.c                          |   6 ++
 revision.h                          |   1 +
 t/t4215-log-skewed-merges.sh        | 144 ++++++++++++++++++++++++++++
 5 files changed, 186 insertions(+), 23 deletions(-)

diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc
index 2d195a1474..d530e744f6 100644
--- a/Documentation/rev-list-options.adoc
+++ b/Documentation/rev-list-options.adoc
@@ -1259,6 +1259,11 @@ This implies the `--topo-order` option by default, but the
 	in between them in that case. If _<barrier>_ is specified, it
 	is the string that will be shown instead of the default one.
 
+`--graph-lane-limit=<n>`::
+	When `--graph` is used, limit the number of graph lanes to be shown.
+	Lanes over the limit are not shown. By default it is set to 0
+	(no limit), zero and negative values are ignored and treated as no limit.
+
 ifdef::git-rev-list[]
 `--count`::
 	Print a number stating how many commits would have been
diff --git a/graph.c b/graph.c
index 70458cf323..ee1f9e2d2d 100644
--- a/graph.c
+++ b/graph.c
@@ -82,8 +82,6 @@ static void graph_show_line_prefix(const struct diff_options *diffopt)
 static const char **column_colors;
 static unsigned short column_colors_max;
 
-static unsigned int max_lanes = 15;
-
 static void parse_graph_colors_config(struct strvec *colors, const char *string)
 {
 	const char *end, *start;
@@ -319,9 +317,13 @@ struct git_graph {
 	struct strbuf prefix_buf;
 };
 
-static inline int graph_needs_truncation(int lane)
+static inline int graph_needs_truncation(struct git_graph *graph, int lane)
 {
-	return lane >= max_lanes;
+	int max = graph->revs->graph_max_lanes;
+	/*
+	 * Ignore values <= 0, meaning no limit.
+	 */
+	return max > 0 && lane >= max;
 }
 
 static const char *diff_output_prefix_callback(struct diff_options *opt, void *data)
@@ -614,7 +616,7 @@ static void graph_update_columns(struct git_graph *graph)
 {
 	struct commit_list *parent;
 	int max_new_columns;
-	int i, seen_this, is_commit_in_columns, max;
+	int i, seen_this, is_commit_in_columns;
 
 	/*
 	 * Swap graph->columns with graph->new_columns
@@ -704,12 +706,17 @@ static void graph_update_columns(struct git_graph *graph)
 	}
 
 	/*
-	 * Cap to the hard-coded limit.
-	 * Allow commits from merges to align to the merged lane.
+	 *  If graph_max_lanes is set, cap the width
 	 */
-	max = max_lanes * 2 + 2;
-	if (graph->width > max)
-		graph->width = max;
+	if (graph->revs->graph_max_lanes > 0) {
+		/*
+		 * Width is column index while a lane is half that.
+		 * Allow commits from merges to align to the merged lane.
+		 */
+		int max_width = graph->revs->graph_max_lanes * 2 + 2;
+		if (graph->width > max_width)
+			graph->width = max_width;
+	}
 
 	/*
 	 * Shrink mapping_size to be the minimum necessary
@@ -861,7 +868,7 @@ static void graph_output_padding_line(struct git_graph *graph,
 	 * Output a padding row, that leaves all branch lines unchanged
 	 */
 	for (i = 0; i < graph->num_new_columns; i++) {
-		if (graph_needs_truncation(i))
+		if (graph_needs_truncation(graph, i))
 			break;
 		graph_line_write_column(line, &graph->new_columns[i], '|');
 		graph_line_addch(line, ' ');
@@ -920,7 +927,7 @@ static void graph_output_pre_commit_line(struct git_graph *graph,
 			seen_this = 1;
 			graph_line_write_column(line, col, '|');
 			graph_line_addchars(line, ' ', graph->expansion_row);
-		} else if (seen_this && graph_needs_truncation(i)) {
+		} else if (seen_this && graph_needs_truncation(graph, i)) {
 			break;
 		} else if (seen_this && (graph->expansion_row == 0)) {
 			/*
@@ -1018,7 +1025,7 @@ static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line
 		 * Commit is at commit_index, each iteration move one lane to
 		 * the right from the commit.
 		 */
-		if (graph_needs_truncation(graph->commit_index + 1 + i))
+		if (graph_needs_truncation(graph, graph->commit_index + 1 + i))
 			break;
 
 		graph_line_write_column(line, col, (i == dashed_parents - 1) ? '.' : '-');
@@ -1055,14 +1062,14 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 			seen_this = 1;
 			graph_output_commit_char(graph, line);
 
-			if (graph_needs_truncation(i)) {
+			if (graph_needs_truncation(graph, i)) {
 				graph_line_addch(line, ' ');
 				break;
 			}
 
 			if (graph->num_parents > 2)
 				graph_draw_octopus_merge(graph, line);
-		} else if (graph_needs_truncation(i)) {
+		} else if (graph_needs_truncation(graph, i)) {
 			seen_this = 1;
 			break;
 		} else if (seen_this && (graph->edges_added > 1)) {
@@ -1112,7 +1119,7 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 	 * padding lane.
 	 */
 	if (graph->num_parents > 1) {
-		if (!graph_needs_truncation(graph->commit_index)) {
+		if (!graph_needs_truncation(graph, graph->commit_index)) {
 			graph_update_state(graph, GRAPH_POST_MERGE);
 		} else {
 			struct commit_list *p = first_interesting_parent(graph);
@@ -1128,7 +1135,7 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 
 			lane = graph_find_new_column_by_commit(graph, p->item);
 
-			if (!graph_needs_truncation(lane))
+			if (!graph_needs_truncation(graph, lane))
 				graph_update_state(graph, GRAPH_POST_MERGE);
 			else if (graph_is_mapping_correct(graph))
 				graph_update_state(graph, GRAPH_PADDING);
@@ -1192,7 +1199,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 				 * comparable with i. Don't truncate if there are
 				 * no more lanes to print (end of the lane)
 				 */
-				if (graph_needs_truncation(j / 2 + i) &&
+				if (graph_needs_truncation(graph, j / 2 + i) &&
 				    j / 2 + i <= graph->num_columns) {
 					if ((j + i * 2) % 2 != 0)
 						graph_line_addch(line, ' ');
@@ -1205,7 +1212,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 					 * Check if the next lane needs truncation
 					 * to avoid having the padding doubled
 					 */
-					if (graph_needs_truncation((j + 1) / 2 + i) &&
+					if (graph_needs_truncation(graph, (j + 1) / 2 + i) &&
 					    j < graph->num_parents - 1) {
 						truncated = 1;
 						break;
@@ -1220,7 +1227,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 				break;
 			if (graph->edges_added == 0)
 				graph_line_addch(line, ' ');
-		} else if (graph_needs_truncation(i)) {
+		} else if (graph_needs_truncation(graph, i)) {
 			break;
 		} else if (seen_this) {
 			if (graph->edges_added > 0)
@@ -1231,7 +1238,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 			 * If it's between two lanes and next would be truncated,
 			 * don't add space padding.
 			 */
-			if (!graph_needs_truncation(i + 1))
+			if (!graph_needs_truncation(graph, i + 1))
 				graph_line_addch(line, ' ');
 		} else {
 			graph_line_write_column(line, col, '|');
@@ -1380,7 +1387,7 @@ static void graph_output_collapsing_line(struct git_graph *graph, struct graph_l
 	for (i = 0; i < graph->mapping_size; i++) {
 		int target = graph->mapping[i];
 
-		if (!truncated && graph_needs_truncation(i / 2)) {
+		if (!truncated && graph_needs_truncation(graph, i / 2)) {
 			truncated = 1;
 		}
 
@@ -1480,7 +1487,7 @@ static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
 	for (i = 0; i < graph->num_columns; i++) {
 		struct column *col = &graph->columns[i];
 
-		if (graph_needs_truncation(i))
+		if (graph_needs_truncation(graph, i))
 			break;
 
 		graph_line_write_column(&line, col, '|');
diff --git a/revision.c b/revision.c
index 31808e3df0..81b67682a8 100644
--- a/revision.c
+++ b/revision.c
@@ -2605,6 +2605,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--no-graph")) {
 		graph_clear(revs->graph);
 		revs->graph = NULL;
+	} else if (skip_prefix(arg, "--graph-lane-limit=", &optarg)) {
+		revs->graph_max_lanes = parse_count(optarg);
 	} else if (!strcmp(arg, "--encode-email-headers")) {
 		revs->encode_email_headers = 1;
 	} else if (!strcmp(arg, "--no-encode-email-headers")) {
@@ -3172,6 +3174,10 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 
 	if (revs->no_walk && revs->graph)
 		die(_("options '%s' and '%s' cannot be used together"), "--no-walk", "--graph");
+
+	if (revs->graph_max_lanes > 0 && !revs->graph)
+		die(_("the option '%s' requires '%s'"), "--graph-lane-limit", "--graph");
+
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die(_("the option '%s' requires '%s'"), "--grep-reflog", "--walk-reflogs");
 
diff --git a/revision.h b/revision.h
index 69242ecb18..874ccce625 100644
--- a/revision.h
+++ b/revision.h
@@ -304,6 +304,7 @@ struct rev_info {
 
 	/* Display history graph */
 	struct git_graph *graph;
+	int graph_max_lanes;
 
 	/* special limits */
 	int skip_count;
diff --git a/t/t4215-log-skewed-merges.sh b/t/t4215-log-skewed-merges.sh
index 28d0779a8c..d7524e9366 100755
--- a/t/t4215-log-skewed-merges.sh
+++ b/t/t4215-log-skewed-merges.sh
@@ -370,4 +370,148 @@ test_expect_success 'log --graph with multiple tips' '
 	EOF
 '
 
+test_expect_success 'log --graph --graph-lane-limit=2 limited to two lanes' '
+	check_graph --graph-lane-limit=2 M_7 <<-\EOF
+	*-.   7_M4
+	|\ \
+	| | * 7_G
+	| | * 7_F
+	| *   7_E
+	| *   7_D
+	* |   7_C
+	| |/
+	|/|
+	* | 7_B
+	|/
+	* 7_A
+	EOF
+'
+
+test_expect_success 'log --graph --graph-lane-limit=1 truncate mid octopus merge' '
+	check_graph --graph-lane-limit=1 M_7 <<-\EOF
+	*-  7_M4
+	|\
+	|   7_G
+	|   7_F
+	| * 7_E
+	| * 7_D
+	*   7_C
+	|
+	|/
+	*   7_B
+	|/
+	* 7_A
+	EOF
+'
+
+test_expect_success 'log --graph --graph-lane-limit=3 limited to three lanes' '
+	check_graph --graph-lane-limit=3 M_1 M_3 M_5 M_7 <<-\EOF
+	*   7_M1
+	|\
+	| | *   7_M2
+	| | |\
+	| | | * 7_H
+	| | |   7_M3
+	| | |   7_J
+	| | |   7_I
+	| | |   7_M4
+	| |_|_
+	|/| |
+	| | |_
+	| |/|
+	| | |
+	| | |/
+	| | *   7_G
+	| | |
+	| | |/
+	| | *   7_F
+	| * |   7_E
+	| | |/
+	| |/|
+	| * |   7_D
+	| | |/
+	| |/|
+	* | | 7_C
+	| |/
+	|/|
+	* | 7_B
+	|/
+	* 7_A
+	EOF
+'
+
+test_expect_success 'log --graph --graph-lane-limit=6 check if it only shows first of 3 parent merge' '
+	check_graph --graph-lane-limit=6 M_1 M_3 M_5 M_7 <<-\EOF
+	*   7_M1
+	|\
+	| | *   7_M2
+	| | |\
+	| | | * 7_H
+	| | | | *   7_M3
+	| | | | |\
+	| | | | | * 7_J
+	| | | | * | 7_I
+	| | | | | | * 7_M4
+	| |_|_|_|_|/
+	|/| | | | |/
+	| | |_|_|/|
+	| |/| | | |/
+	| | | |_|/|
+	| | |/| | |
+	| | * | | | 7_G
+	| | | |_|/
+	| | |/| |
+	| | * | | 7_F
+	| * | | | 7_E
+	| | |/ /
+	| |/| |
+	| * | | 7_D
+	| | |/
+	| |/|
+	* | | 7_C
+	| |/
+	|/|
+	* | 7_B
+	|/
+	* 7_A
+	EOF
+'
+
+test_expect_success 'log --graph --graph-lane-limit=7 check if it shows all 3 parent merge' '
+	check_graph --graph-lane-limit=7 M_1 M_3 M_5 M_7 <<-\EOF
+	*   7_M1
+	|\
+	| | *   7_M2
+	| | |\
+	| | | * 7_H
+	| | | | *   7_M3
+	| | | | |\
+	| | | | | * 7_J
+	| | | | * | 7_I
+	| | | | | | *   7_M4
+	| |_|_|_|_|/|\
+	|/| | | | |/ /
+	| | |_|_|/| /
+	| |/| | | |/
+	| | | |_|/|
+	| | |/| | |
+	| | * | | | 7_G
+	| | | |_|/
+	| | |/| |
+	| | * | | 7_F
+	| * | | | 7_E
+	| | |/ /
+	| |/| |
+	| * | | 7_D
+	| | |/
+	| |/|
+	* | | 7_C
+	| |/
+	|/|
+	* | 7_B
+	|/
+	* 7_A
+	EOF
+'
+
 test_done

From 9bab3ce5553b2333b8f8ee1aff27a9fe6a938f65 Mon Sep 17 00:00:00 2001
From: Pablo Sabater <pabloosabaterr@gmail.com>
Date: Sat, 28 Mar 2026 01:11:13 +0100
Subject: [PATCH 3/3] graph: add truncation mark to capped lanes

When lanes are hidden by --graph-lane-limit, show a "~"
truncation mark, so users know that there are lanes
being truncated. The "~" is chosen because it is not
used elsewhere in the graph and it is discrete.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/rev-list-options.adoc |  5 ++-
 graph.c                             | 22 +++++++---
 t/t4215-log-skewed-merges.sh        | 64 ++++++++++++++---------------
 3 files changed, 52 insertions(+), 39 deletions(-)

diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc
index d530e744f6..94a7b1c065 100644
--- a/Documentation/rev-list-options.adoc
+++ b/Documentation/rev-list-options.adoc
@@ -1261,8 +1261,9 @@ This implies the `--topo-order` option by default, but the
 
 `--graph-lane-limit=<n>`::
 	When `--graph` is used, limit the number of graph lanes to be shown.
-	Lanes over the limit are not shown. By default it is set to 0
-	(no limit), zero and negative values are ignored and treated as no limit.
+	Lanes over the limit are replaced with a truncation mark '~'.
+	By default it is set to 0 (no limit), zero and negative values
+	are ignored and treated as no limit.
 
 ifdef::git-rev-list[]
 `--count`::
diff --git a/graph.c b/graph.c
index ee1f9e2d2d..842282685f 100644
--- a/graph.c
+++ b/graph.c
@@ -706,11 +706,11 @@ static void graph_update_columns(struct git_graph *graph)
 	}
 
 	/*
-	 *  If graph_max_lanes is set, cap the width
+	 * If graph_max_lanes is set, cap the width
 	 */
 	if (graph->revs->graph_max_lanes > 0) {
 		/*
-		 * Width is column index while a lane is half that.
+		 * width of "| " per lanes plus truncation mark "~ ".
 		 * Allow commits from merges to align to the merged lane.
 		 */
 		int max_width = graph->revs->graph_max_lanes * 2 + 2;
@@ -868,8 +868,10 @@ static void graph_output_padding_line(struct git_graph *graph,
 	 * Output a padding row, that leaves all branch lines unchanged
 	 */
 	for (i = 0; i < graph->num_new_columns; i++) {
-		if (graph_needs_truncation(graph, i))
+		if (graph_needs_truncation(graph, i)) {
+			graph_line_addstr(line, "~ ");
 			break;
+		}
 		graph_line_write_column(line, &graph->new_columns[i], '|');
 		graph_line_addch(line, ' ');
 	}
@@ -928,6 +930,7 @@ static void graph_output_pre_commit_line(struct git_graph *graph,
 			graph_line_write_column(line, col, '|');
 			graph_line_addchars(line, ' ', graph->expansion_row);
 		} else if (seen_this && graph_needs_truncation(graph, i)) {
+			graph_line_addstr(line, "~ ");
 			break;
 		} else if (seen_this && (graph->expansion_row == 0)) {
 			/*
@@ -1025,8 +1028,10 @@ static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line
 		 * Commit is at commit_index, each iteration move one lane to
 		 * the right from the commit.
 		 */
-		if (graph_needs_truncation(graph, graph->commit_index + 1 + i))
+		if (graph_needs_truncation(graph, graph->commit_index + 1 + i)) {
+			graph_line_addstr(line, "~ ");
 			break;
+		}
 
 		graph_line_write_column(line, col, (i == dashed_parents - 1) ? '.' : '-');
 	}
@@ -1070,6 +1075,7 @@ static void graph_output_commit_line(struct git_graph *graph, struct graph_line
 			if (graph->num_parents > 2)
 				graph_draw_octopus_merge(graph, line);
 		} else if (graph_needs_truncation(graph, i)) {
+			graph_line_addstr(line, "~ ");
 			seen_this = 1;
 			break;
 		} else if (seen_this && (graph->edges_added > 1)) {
@@ -1203,6 +1209,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 				    j / 2 + i <= graph->num_columns) {
 					if ((j + i * 2) % 2 != 0)
 						graph_line_addch(line, ' ');
+					graph_line_addstr(line, "~ ");
 					truncated = 1;
 					break;
 				}
@@ -1214,6 +1221,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 					 */
 					if (graph_needs_truncation(graph, (j + 1) / 2 + i) &&
 					    j < graph->num_parents - 1) {
+						graph_line_addstr(line, "~ ");
 						truncated = 1;
 						break;
 					} else if (graph->edges_added > 0 || j < graph->num_parents - 1)
@@ -1228,6 +1236,7 @@ static void graph_output_post_merge_line(struct git_graph *graph, struct graph_l
 			if (graph->edges_added == 0)
 				graph_line_addch(line, ' ');
 		} else if (graph_needs_truncation(graph, i)) {
+			graph_line_addstr(line, "~ ");
 			break;
 		} else if (seen_this) {
 			if (graph->edges_added > 0)
@@ -1388,6 +1397,7 @@ static void graph_output_collapsing_line(struct git_graph *graph, struct graph_l
 		int target = graph->mapping[i];
 
 		if (!truncated && graph_needs_truncation(graph, i / 2)) {
+			graph_line_addstr(line, "~ ");
 			truncated = 1;
 		}
 
@@ -1487,8 +1497,10 @@ static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
 	for (i = 0; i < graph->num_columns; i++) {
 		struct column *col = &graph->columns[i];
 
-		if (graph_needs_truncation(graph, i))
+		if (graph_needs_truncation(graph, i)) {
+			graph_line_addstr(&line, "~ ");
 			break;
+		}
 
 		graph_line_write_column(&line, col, '|');
 
diff --git a/t/t4215-log-skewed-merges.sh b/t/t4215-log-skewed-merges.sh
index d7524e9366..1612f05f1b 100755
--- a/t/t4215-log-skewed-merges.sh
+++ b/t/t4215-log-skewed-merges.sh
@@ -376,9 +376,9 @@ test_expect_success 'log --graph --graph-lane-limit=2 limited to two lanes' '
 	|\ \
 	| | * 7_G
 	| | * 7_F
-	| *   7_E
-	| *   7_D
-	* |   7_C
+	| * ~ 7_E
+	| * ~ 7_D
+	* | ~ 7_C
 	| |/
 	|/|
 	* | 7_B
@@ -389,16 +389,16 @@ test_expect_success 'log --graph --graph-lane-limit=2 limited to two lanes' '
 
 test_expect_success 'log --graph --graph-lane-limit=1 truncate mid octopus merge' '
 	check_graph --graph-lane-limit=1 M_7 <<-\EOF
-	*-  7_M4
-	|\
-	|   7_G
-	|   7_F
+	*-~  7_M4
+	|\~
+	| ~ 7_G
+	| ~ 7_F
 	| * 7_E
 	| * 7_D
-	*   7_C
-	|
-	|/
-	*   7_B
+	* ~ 7_C
+	| ~
+	|/~
+	* ~ 7_B
 	|/
 	* 7_A
 	EOF
@@ -411,24 +411,24 @@ test_expect_success 'log --graph --graph-lane-limit=3 limited to three lanes' '
 	| | *   7_M2
 	| | |\
 	| | | * 7_H
-	| | |   7_M3
-	| | |   7_J
-	| | |   7_I
-	| | |   7_M4
-	| |_|_
-	|/| |
-	| | |_
-	| |/|
-	| | |
-	| | |/
-	| | *   7_G
-	| | |
-	| | |/
-	| | *   7_F
-	| * |   7_E
-	| | |/
-	| |/|
-	| * |   7_D
+	| | | ~ 7_M3
+	| | | ~ 7_J
+	| | | ~ 7_I
+	| | | ~ 7_M4
+	| |_|_~
+	|/| | ~
+	| | |_~
+	| |/| ~
+	| | | ~
+	| | |/~
+	| | * ~ 7_G
+	| | | ~
+	| | |/~
+	| | * ~ 7_F
+	| * | ~ 7_E
+	| | |/~
+	| |/| ~
+	| * | ~ 7_D
 	| | |/
 	| |/|
 	* | | 7_C
@@ -452,9 +452,9 @@ test_expect_success 'log --graph --graph-lane-limit=6 check if it only shows fir
 	| | | | | * 7_J
 	| | | | * | 7_I
 	| | | | | | * 7_M4
-	| |_|_|_|_|/
-	|/| | | | |/
-	| | |_|_|/|
+	| |_|_|_|_|/~
+	|/| | | | |/~
+	| | |_|_|/| ~
 	| |/| | | |/
 	| | | |_|/|
 	| | |/| | |