[PATCH 1/1] Fix --stat width calculations to handle --graph

[Lucian Poston <lucian.poston@gmail.com>]

Adjusted stat width calculations to take into consideration the diff output
prefix e.g. the graph prefix generated by `git log --graph --stat`.

This change fixes the line wrapping that occurs when diff stats are large
enough to be scaled to fit within the terminal's columns. This issue only
appears when using --stat and --graph together on large diffs.

Adjusted stat output tests accordingly. The scaled output tests are closer to
the target 5:3 ratio.

Added test that verifies the output of --stat --graph is truncated to fit
within the available terminal $COLUMNS

Signed-off-by: Lucian Poston <lucian.poston@gmail.com>
---
 diff.c                 |   55 ++++++++++++++++++++++++++++++++---------------
 t/t4052-stat-output.sh |   24 +++++++++++++++++++-
 2 files changed, 59 insertions(+), 20 deletions(-)

diff --git a/diff.c b/diff.c
index 377ec1e..3a26561 100644
--- a/diff.c
+++ b/diff.c
@@ -1382,7 +1382,9 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	int total_files = data->nr;
 	int width, name_width, graph_width, number_width = 4, count;
 	const char *reset, *add_c, *del_c;
-	const char *line_prefix = "";
+	const char *line_prefix = "", *line_prefix_iter;
+	unsigned int line_prefix_length = 0;
+	unsigned int reserved_character_count;
 	int extra_shown = 0;
 	struct strbuf *msg = NULL;
 
@@ -1392,6 +1394,18 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	if (options->output_prefix) {
 		msg = options->output_prefix(options, options->output_prefix_data);
 		line_prefix = msg->buf;
+
+		/*
+		 * line_prefix can contain color codes, so only pipes '|' and
+		 * spaces ' ' are counted.
+		 */
+		line_prefix_iter = line_prefix;
+		while (*line_prefix_iter != '\0') {
+			if (*line_prefix_iter == ' ' || *line_prefix_iter == '|') {
+				line_prefix_length++;
+			}
+			line_prefix_iter += 1;
+		}
 	}
 
 	count = options->stat_count ? options->stat_count : data->nr;
@@ -1427,22 +1441,27 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	 * 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 want a maximum of min(max_change, stat_graph_width) for the +- 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).
+	 * Each line needs space for the following characters:
+	 *   - line_prefix_length for the line_prefix
+	 *   - 1 for the initial " "
+	 *   - 4 + decimal_width(max_change) for " | NNNN "
+	 *   - 1 for the empty column at the end,
+	 * Altogether, the reserved_character_count totals
+	 * 6 + line_prefix_length + 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, but no more
+	 * and the rest for reserved characters + graph part, but no more
 	 * than stat_graph_width for the graph part.
-	 * (5/8 gives 50 for filename and 30 for the constant parts + graph
-	 * for the standard terminal size).
+	 * (5/8 gives 50 for filename and 30 for the reserved characters + graph
+	 * for the standard terminal size assuming there is no line prefix).
 	 *
 	 * 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.
 	 */
+	reserved_character_count = 6 + number_width + line_prefix_length;
 
 	if (options->stat_width == -1)
 		width = term_columns();
@@ -1453,11 +1472,11 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		options->stat_graph_width = diff_stat_graph_width;
 
 	/*
-	 * Guarantee 3/8*16==6 for the graph part
-	 * and 5/8*16==10 for the filename part
+	 * Guarantees at least 6 characters for the graph part [16 * 3/8]
+	 * and at least 10 for the filename part [16 * 5/8]
 	 */
-	if (width < 16 + 6 + number_width)
-		width = 16 + 6 + number_width;
+	if (width < 16 + reserved_character_count)
+		width = 16 + reserved_character_count;
 
 	/*
 	 * First assign sizes that are wanted, ignoring available width.
@@ -1472,16 +1491,16 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	/*
 	 * 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 (reserved_character_count + name_width + graph_width > width) {
+		if (graph_width > (width - reserved_character_count) * 3/8)
+			graph_width = (width - reserved_character_count) * 3/8;
 		if (options->stat_graph_width &&
-		    graph_width > options->stat_graph_width)
+				graph_width > options->stat_graph_width)
 			graph_width = options->stat_graph_width;
-		if (name_width > width - number_width - 6 - graph_width)
-			name_width = width - number_width - 6 - graph_width;
+		if (name_width > width - reserved_character_count - graph_width)
+			name_width = width - reserved_character_count - graph_width;
 		else
-			graph_width = width - number_width - 6 - name_width;
+			graph_width = width - reserved_character_count - name_width;
 	}
 
 	/*
diff --git a/t/t4052-stat-output.sh b/t/t4052-stat-output.sh
index 328aa8f..84dd8bb 100755
--- a/t/t4052-stat-output.sh
+++ b/t/t4052-stat-output.sh
@@ -162,7 +162,7 @@ test_expect_success 'preparation for long filename tests' '
 '
 
 cat >expect <<'EOF'
- ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++
+ ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++
 EOF
 while read cmd args
 do
@@ -179,7 +179,7 @@ log -1 --stat
 EOF
 
 cat >expect80 <<'EOF'
- ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++++
+ ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++++++++++
 EOF
 cat >expect200 <<'EOF'
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
@@ -198,6 +198,26 @@ respects expect200 show --stat
 respects expect200 log -1 --stat
 EOF
 
+cat >expect80graphed <<'EOF'
+|  ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 +++++++++++++++++++++++++
+EOF
+cat >expect80 <<'EOF'
+ ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++++++++++
+EOF
+while read verb expect cmd args
+do
+	test_expect_success "$cmd $verb 80 COLUMNS (long filename)" '
+		COLUMNS=80 git $cmd $args >output
+		grep " | " output >actual &&
+		test_cmp "$expect" actual
+	'
+done <<\EOF
+respects expect80 show --stat
+respects expect80 log -1 --stat
+respects expect80graphed show --stat --graph
+respects expect80graphed log -1 --stat --graph
+EOF
+
 cat >expect <<'EOF'
  abcd | 1000 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 EOF
-- 
1.7.3.4