Add navigation between merge commits

Allow skipping forward and backward between merge commits by means of
two actions “move-next-merge” and “move-prev-merge”. The search
considers all lines containing the merge symbol.

NEWS.adoc

@@ -8,6 +8,7 @@ Improvements:
 
  - Support Git's 'diff-highlight' program when `diff-highlight` is set to either
    true or the path of the script to use for post-processing.
+ - Add navigation between merge commits. (GH #525)
  - Add 'A' as a binding to apply a stash without dropping it.
  - Bind 'Ctrl-D' and 'Ctrl-U' to half-page movements by default.
  - manual: Mention how to change default Up/Down behavior in diff view.

include/tig/graph.h

@@ -39,6 +39,7 @@ struct graph {
 			   const char *id, const char *parents, bool is_boundary);
 	bool (*add_parent)(struct graph *graph, const char *parent);
 	bool (*render_parents)(struct graph *graph, struct graph_canvas *canvas);
+	bool (*is_merge)(struct graph_canvas *canvas);
 
 	void (*foreach_symbol)(const struct graph *graph, const struct graph_canvas *canvas, graph_symbol_iterator_fn fn, void *data);
 

include/tig/request.h

@@ -54,6 +54,8 @@
 	REQ_(MOVE_HALF_PAGE_UP,	"Move cursor one page up"), \
 	REQ_(MOVE_FIRST_LINE,	"Move cursor to first line"), \
 	REQ_(MOVE_LAST_LINE,	"Move cursor to last line"), \
+	REQ_(MOVE_NEXT_MERGE,	"Move cursor to next merge commit"), \
+	REQ_(MOVE_PREV_MERGE,	"Move cursor to previous merge commit"), \
 	\
 	REQ_GROUP("Scrolling") \
 	REQ_(SCROLL_LINE_UP,	"Scroll one line up"), \

include/tig/search.h

@@ -19,6 +19,7 @@
 void reset_search(struct view *view);
 void search_view(struct view *view, enum request request);
 void find_next(struct view *view, enum request request);
+void find_merge(struct view *view, enum request request);
 bool grep_text(struct view *view, const char *text[]);
 
 #endif

src/graph-v1.c

@@ -312,6 +312,12 @@ graph_render_parents(struct graph *graph_, struct graph_canvas *canvas)
 	return true;
 }
 
+static bool
+graph_is_merge(struct graph_canvas *canvas)
+{
+	return !!canvas->symbols->merge;
+}
+
 static bool
 graph_add_commit(struct graph *graph_, struct graph_canvas *canvas,
 		 const char *id, const char *parents, bool is_boundary)
@@ -493,6 +499,7 @@ init_graph_v1(void)
 	api->add_commit = graph_add_commit;
 	api->add_parent = graph_add_parent;
 	api->render_parents = graph_render_parents;
+	api->is_merge = graph_is_merge;
 	api->foreach_symbol = graph_foreach_symbol;
 	api->symbol_to_ascii = graph_symbol_to_ascii;
 	api->symbol_to_utf8 = graph_symbol_to_utf8;

src/graph-v2.c

@@ -713,6 +713,12 @@ graph_render_parents(struct graph *graph_ref, struct graph_canvas *canvas)
 	return true;
 }
 
+static bool
+graph_is_merge(struct graph_canvas *canvas)
+{
+	return !!canvas->symbols->merge;
+}
+
 static bool
 graph_add_commit(struct graph *graph_ref, struct graph_canvas *canvas,
 		 const char *id, const char *parents, bool is_boundary)
@@ -1109,6 +1115,7 @@ init_graph_v2(void)
 	api->done_rendering = done_graph_rendering;
 	api->add_commit = graph_add_commit;
 	api->add_parent = graph_add_parent;
+	api->is_merge = graph_is_merge;
 	api->render_parents = graph_render_parents;
 	api->foreach_symbol = graph_foreach_symbol;
 	api->symbol_to_ascii = graph_symbol_to_ascii;

src/main.c

@@ -24,6 +24,7 @@
 #include "tig/stage.h"
 #include "tig/main.h"
 #include "tig/diff.h"
+#include "tig/search.h"
 
 /*
  * Main view backend
@@ -536,6 +537,11 @@ main_request(struct view *view, enum request request, struct line *line)
 		goto_id(view, "%(commit)^", true, false);
 		break;
 
+	case REQ_MOVE_NEXT_MERGE:
+	case REQ_MOVE_PREV_MERGE:
+		find_merge(view, request);
+		break;
+
 	default:
 		return request;
 	}

src/search.c

@@ -15,6 +15,8 @@
 #include "tig/prompt.h"
 #include "tig/display.h"
 #include "tig/draw.h"
+#include "tig/main.h"
+#include "tig/graph.h"
 
 DEFINE_ALLOCATOR(realloc_unsigned_ints, unsigned int, 32)
 
@@ -159,6 +161,77 @@ find_next(struct view *view, enum request request)
 	report("%s", get_status_message(code));
 }
 
+static enum status_code
+find_next_merge_line(struct view *view, int direction, bool wrapped)
+{
+	enum status_code code = -1;
+	int dist;
+	size_t max;
+
+	if (wrapped)
+		max = view->lines;
+	else
+		max = direction > 0 ? view->lines - view->pos.lineno
+				    : view->pos.lineno;
+
+	for (dist = direction; abs(dist) < max; dist += direction) {
+		ssize_t lineno = view->pos.lineno + dist;
+		if (lineno < 0)
+			lineno += view->lines;
+		else if (lineno >= view->lines)
+			lineno -= view->lines;
+
+		struct line *line = &view->line[lineno];
+		struct commit *commit = line->data;
+		struct graph_canvas *canvas = &commit->graph;
+		struct view_column_data column_data;
+
+		if (!view->ops->get_column_data(view, line, &column_data))
+			continue;
+
+		if (column_data.graph && !column_data.graph->is_merge(canvas))
+			continue;
+
+		select_view_line(view, lineno);
+		code = SUCCESS;
+		break;
+	}
+
+	return code;
+}
+
+static enum status_code
+find_next_merge(struct view *view, enum request request)
+{
+	int direction;
+	enum status_code code;
+
+	switch (request) {
+	case REQ_MOVE_NEXT_MERGE:
+		direction = 1;
+		break;
+
+	case REQ_MOVE_PREV_MERGE:
+		direction = -1;
+		break;
+
+	default:
+		return error("Invalid request searching for next merge");
+	}
+
+	code = find_next_merge_line(view, direction, opt_wrap_search);
+
+	return code == SUCCESS ? code : success("No merge commit found");
+}
+
+void
+find_merge(struct view *view, enum request request)
+{
+	enum status_code code = find_next_merge(view, request);
+
+	report("%s", get_status_message(code));
+}
+
 void
 reset_search(struct view *view)
 {

src/tig.c

@@ -292,6 +292,11 @@ view_driver(struct view *view, enum request request)
 		find_next(view, request);
 		break;
 
+	case REQ_MOVE_NEXT_MERGE:
+	case REQ_MOVE_PREV_MERGE:
+		report("Moving between merge commits is not supported by the %s view", view->name);
+		break;
+
 	case REQ_STOP_LOADING:
 		foreach_view(view, i) {
 			if (view->pipe)