diff --stat: use a maximum of 5/8 for the filename part

The way that available columns are divided between the filename part
and the graph part is modified to use as many columns as necessary for
the filenames and the rest for the graph.

If there isn't enough columns to print both the filename and the
graph, at least 5/8 of available space is devoted to filenames. On a
standard 80 column terminal, or if not connected to a terminal and
using the default of 80 columns, this gives the same partition as
before.

The effect of this change is visible in the patch to the test vector
in t4052; with a small change with long filename, it stops truncating
the name part too short, and also allocates a bit more columns to the
graph for larger changes.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 60 insertions, 30 deletions

diff --git a/diff.c b/diff.c
index 74782770bc..1656310ddc 100644
--- a/diff.c
+++ b/diff.c
@@ -1329,7 +1329,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	int i, len, add, del, adds = 0, dels = 0;
 	uintmax_t max_change = 0, max_len = 0;
 	int total_files = data->nr;
-	int width, name_width, count;
+	int width, name_width, graph_width, number_width = 4, count;
 	const char *reset, *add_c, *del_c;
 	const char *line_prefix = "";
 	int extra_shown = 0;
@@ -1343,28 +1343,15 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		line_prefix = msg->buf;
 	}
 
-	if (options->stat_width == -1)
-		width = term_columns();
-	else
-		width = options->stat_width ? options->stat_width : 80;
-	name_width = options->stat_name_width ? options->stat_name_width : 50;
 	count = options->stat_count ? options->stat_count : data->nr;
 
-	/* Sanity: give at least 5 columns to the graph,
-	 * but leave at least 10 columns for the name.
-	 */
-	if (width < 25)
-		width = 25;
-	if (name_width < 10)
-		name_width = 10;
-	else if (width < name_width + 15)
-		name_width = width - 15;
-
-	/* Find the longest filename and max number of changes */
 	reset = diff_get_color_opt(options, DIFF_RESET);
 	add_c = diff_get_color_opt(options, DIFF_FILE_NEW);
 	del_c = diff_get_color_opt(options, DIFF_FILE_OLD);
 
+	/*
+	 * Find the longest filename and max number of changes
+	 */
 	for (i = 0; (i < count) && (i < data->nr); i++) {
 		struct diffstat_file *file = data->files[i];
 		uintmax_t change = file->added + file->deleted;
@@ -1385,19 +1372,62 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	}
 	count = i; /* min(count, data->nr) */
 
-	/* Compute the width of the graph part;
-	 * 10 is for one blank at the beginning of the line plus
-	 * " | count " between the name and the graph.
+	/*
+	 * We have width = stat_width or term_columns() columns total.
+	 * We want a maximum of min(max_len, stat_name_width) for the name part.
+	 * We also need 1 for " " and 4 + decimal_width(max_change)
+	 * for " | NNNN " and one the empty column at the end, altogether
+	 * 6 + decimal_width(max_change).
+	 *
+	 * If there's not enough space, we will use the smaller of
+	 * stat_name_width (if set) and 5/8*width for the filename,
+	 * and the rest for constant elements + graph part.
+	 * (5/8 gives 50 for filename and 30 for the constant parts + graph
+	 * for the standard terminal size).
 	 *
-	 * From here on, name_width is the width of the name area,
-	 * and width is the width of the graph area.
+	 * In other words: stat_width limits the maximum width, and
+	 * stat_name_width fixes the maximum width of the filename,
+	 * and is also used to divide available columns if there
+	 * aren't enough.
 	 */
-	name_width = (name_width < max_len) ? name_width : max_len;
-	if (width < (name_width + 10) + max_change)
-		width = width - (name_width + 10);
+
+	if (options->stat_width == -1)
+		width = term_columns();
 	else
-		width = max_change;
+		width = options->stat_width ? options->stat_width : 80;
 
+	/*
+	 * Guarantee 3/8*16==6 for the graph part
+	 * and 5/8*16==10 for the filename part
+	 */
+	if (width < 16 + 6 + number_width)
+		width = 16 + 6 + number_width;
+
+	/*
+	 * First assign sizes that are wanted, ignoring available width.
+	 */
+	graph_width = max_change;
+	name_width = (options->stat_name_width > 0 &&
+		      options->stat_name_width < max_len) ?
+		options->stat_name_width : max_len;
+
+	/*
+	 * Adjust adjustable widths not to exceed maximum width
+	 */
+	if (name_width + number_width + 6 + graph_width > width) {
+		if (graph_width > width * 3/8 - number_width - 6)
+			graph_width = width * 3/8 - number_width - 6;
+		if (name_width > width - number_width - 6 - graph_width)
+			name_width = width - number_width - 6 - graph_width;
+		else
+			graph_width = width - number_width - 6 - name_width;
+	}
+
+	/*
+	 * From here name_width is the width of the name area,
+	 * and graph_width is the width of the graph area.
+	 * max_change is used to scale graph properly.
+	 */
 	for (i = 0; i < count; i++) {
 		const char *prefix = "";
 		char *name = data->files[i]->print_name;
@@ -1453,18 +1483,18 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		adds += add;
 		dels += del;
 
-		if (width <= max_change) {
+		if (graph_width <= max_change) {
 			int total = add + del;
 
-			total = scale_linear(add + del, width, max_change);
+			total = scale_linear(add + del, graph_width, max_change);
 			if (total < 2 && add && del)
 				/* width >= 2 due to the sanity check */
 				total = 2;
 			if (add < del) {
-				add = scale_linear(add, width, max_change);
+				add = scale_linear(add, graph_width, max_change);
 				del = total - add;
 			} else {
-				del = scale_linear(del, width, max_change);
+				del = scale_linear(del, graph_width, max_change);
 				add = total - del;
 			}
 		}