diff --stat: add config option to limit graph width

Config option diff.statGraphWidth=<width> is equivalent to
--stat-graph-width=<width>, except that the config option is ignored
by format-patch.

For the graph-width limiting to be usable, it should happen
'automatically' once configured, hence the config option.
Nevertheless, graph width limiting only makes sense when used on a
wide terminal, so it should not influence the output of format-patch,
which adheres to the 80-column standard.
Signed-off-by: NZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/diff-config.txt

@@ -52,6 +52,10 @@ directories with less than 10% of the total amount of changed files,
 and accumulating child directory counts in the parent directories:
 `files,10,cumulative`.
 
+diff.statGraphWidth::
+	Limit the width of the graph part in --stat output. If set, applies
+	to all commands generating --stat outuput except format-patch.
+
 diff.external::
 	If this config variable is set, diff generation is not
 	performed using the internal diff machinery, but using the

Documentation/diff-options.txt

@@ -54,13 +54,15 @@ endif::git-format-patch[]
 
 --stat[=<width>[,<name-width>[,<count>]]]::
 	Generate a diffstat. By default, as much space as necessary
-	will be used for the filename part, and the rest for
-	the graph part. Maximum width defaults to terminal width,
-	or 80 columns if not connected to a terminal, and can be
-	overriden by `<width>`. The width of the filename part can be
-	limited by giving another width `<name-width>` after a comma.
-	The width of the graph part can be limited by using
-	`--stat-graph-width=<width>`.
+	will be used for the filename part, and the rest for the graph
+	part. Maximum width defaults to terminal width, or 80 columns
+	if not connected to a terminal, and can be overriden by
+	`<width>`. The width of the filename part can be limited by
+	giving another width `<name-width>` after a comma. The width
+	of the graph part can be limited by using
+	`--stat-graph-width=<width>` (affects all commands generating
+	a stat graph) or by setting `diff.statGraphWidth=<width>`
+	(does not affect `git format-patch`).
 	By giving a third parameter `<count>`, you can limit the
 	output to the first `<count>` lines, followed by `...` if
 	there are more.

builtin/diff.c

@@ -285,8 +285,9 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	/* Otherwise, we are doing the usual "git" diff */
 	rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;
 
-	/* Scale to real terminal size */
+	/* Scale to real terminal size and respect statGraphWidth config */
 	rev.diffopt.stat_width = -1;
+	rev.diffopt.stat_graph_width = -1;
 
 	/* Default to let external and textconv be used */
 	DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);

builtin/log.c

@@ -78,6 +78,7 @@ static void cmd_log_init_defaults(struct rev_info *rev)
 	rev->verbose_header = 1;
 	DIFF_OPT_SET(&rev->diffopt, RECURSIVE);
 	rev->diffopt.stat_width = -1; /* use full terminal width */
+	rev->diffopt.stat_graph_width = -1; /* respect statGraphWidth config */
 	rev->abbrev_commit = default_abbrev_commit;
 	rev->show_root_diff = default_show_root;
 	rev->subject_prefix = fmt_patch_subject_prefix;

builtin/merge.c

@@ -400,6 +400,7 @@ static void finish(struct commit *head_commit,
 		struct diff_options opts;
 		diff_setup(&opts);
 		opts.stat_width = -1; /* use full terminal width */
+		opts.stat_graph_width = -1; /* respect statGraphWidth config */
 		opts.output_format |=
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;

contrib/completion/git-completion.bash

@@ -2118,6 +2118,7 @@ _git_config ()
 		core.whitespace
 		core.worktree
 		diff.autorefreshindex
+		diff.statGraphWidth
 		diff.external
 		diff.ignoreSubmodules
 		diff.mnemonicprefix

diff.c

@@ -31,6 +31,7 @@ static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;
 static int diff_mnemonic_prefix;
 static int diff_no_prefix;
+static int diff_stat_graph_width;
 static int diff_dirstat_permille_default = 30;
 static struct diff_options default_diff_options;
 
@@ -156,6 +157,10 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		diff_no_prefix = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.statgraphwidth")) {
+		diff_stat_graph_width = git_config_int(var, value);
+		return 0;
+	}
 	if (!strcmp(var, "diff.external"))
 		return git_config_string(&external_diff_cmd_cfg, var, value);
 	if (!strcmp(var, "diff.wordregex"))
@@ -1398,6 +1403,9 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	else
 		width = options->stat_width ? options->stat_width : 80;
 
+	if (options->stat_graph_width == -1)
+		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

t/t4052-stat-output.sh

@@ -112,6 +112,12 @@ do
 		grep " | " output >actual &&
 		test_cmp "$expect" actual
 	'
+
+	test_expect_success "$cmd $verb statGraphWidth config" '
+		git -c diff.statGraphWidth=26 $cmd $args >output
+		grep " | " output >actual &&
+		test_cmp "$expect" actual
+	'
 done <<\EOF
 ignores expect80 format-patch -1 --stdout
 respects expect40 diff HEAD^ HEAD --stat