[PATCH 1/2] diff: introduce --stat-lines to limit the stat lines

[Michael J Gruber <git@drmicha.warpmail.net>]

Often one is interested in the full --stat output only for commits which
change a few files, but not others, because larger restructuring gives a
--stat which fills a few screens.

Introduce a new option --stat-lines=<lines> which limits the --stat output
to the first and last <lines> lines, separated by a "..." line. It can
also be given as the third parameter in
--stat=<width>,<name-width>,<lines>.

Also, the unstuck form is supported analogous to the other two stat
parameters.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
---
I would even consider a default of 10 (i.e. show a 20 line stat in full,
abbreviate larger ones) to be sensible but have refrained from such a
behaviour change.

We have hardcoded defaults for width (80) and name-width (50), so having
one for lines should be okay also. Can I has tis wiz default? ;)
---
 Documentation/diff-options.txt |    5 ++++-
 diff.c                         |   25 +++++++++++++++++++++++--
 diff.h                         |    1 +
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 34f0145..e0429b3 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -48,11 +48,14 @@ endif::git-format-patch[]
 --patience::
 	Generate a diff using the "patience diff" algorithm.
 
---stat[=<width>[,<name-width>]]::
+--stat[=<width>[,<name-width>[,<lines>]]]::
 	Generate a diffstat.  You can override the default
 	output width for 80-column terminal by `--stat=<width>`.
 	The width of the filename part can be controlled by
 	giving another width to it separated by a comma.
+	By giving a third parameter `<lines>`, you can limit the
+	output to the first and last `<lines>` lines, separated by
+	`...`.
 
 --numstat::
 	Similar to `\--stat`, but shows number of added and
diff --git a/diff.c b/diff.c
index feced34..9ccba1e 100644
--- a/diff.c
+++ b/diff.c
@@ -1244,7 +1244,7 @@ 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;
+	int width, name_width, lines;
 	const char *reset, *add_c, *del_c;
 	const char *line_prefix = "";
 	struct strbuf *msg = NULL;
@@ -1259,6 +1259,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 
 	width = options->stat_width ? options->stat_width : 80;
 	name_width = options->stat_name_width ? options->stat_name_width : 50;
+	lines = options->stat_lines;
 
 	/* Sanity: give at least 5 columns to the graph,
 	 * but leave at least 10 columns for the name.
@@ -1303,6 +1304,12 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		width = max_change;
 
 	for (i = 0; i < data->nr; i++) {
+		if (lines && i >= lines && i < data->nr-lines) {
+			fprintf(options->file, "%s ...\n", line_prefix);
+			i = data->nr-lines-1;
+			lines = 0; /* no need to recheck */
+			continue;
+		}
 		const char *prefix = "";
 		char *name = data->files[i]->print_name;
 		uintmax_t added = data->files[i]->added;
@@ -3105,6 +3112,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 	char *end;
 	int width = options->stat_width;
 	int name_width = options->stat_name_width;
+	int lines = options->stat_lines;
 	int argcount = 1;
 
 	arg += strlen("--stat");
@@ -3132,12 +3140,24 @@ static int stat_opt(struct diff_options *options, const char **av)
 				name_width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
+		} else if (!prefixcmp(arg, "-lines")) {
+			arg += strlen("-lines");
+			if (*arg == '=')
+				lines = strtoul(arg + 1, &end, 10);
+			else if (!*arg && !av[1])
+				die("Option '--stat-lines' requires a value");
+			else if (!*arg) {
+				lines = strtoul(av[1], &end, 10);
+				argcount = 2;
+			}
 		}
 		break;
 	case '=':
 		width = strtoul(arg+1, &end, 10);
 		if (*end == ',')
 			name_width = strtoul(end+1, &end, 10);
+		if (*end == ',')
+			lines = strtoul(end+1, &end, 10);
 	}
 
 	/* Important! This checks all the error cases! */
@@ -3146,6 +3166,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 	options->output_format |= DIFF_FORMAT_DIFFSTAT;
 	options->stat_name_width = name_width;
 	options->stat_width = width;
+	options->stat_lines = lines;
 	return argcount;
 }
 
@@ -3191,7 +3212,7 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "-s"))
 		options->output_format |= DIFF_FORMAT_NO_OUTPUT;
 	else if (!prefixcmp(arg, "--stat"))
-		/* --stat, --stat-width, or --stat-name-width */
+		/* --stat, --stat-width, --stat-name-width, or --stat-lines */
 		return stat_opt(options, av);
 
 	/* renames options */
diff --git a/diff.h b/diff.h
index d83e53e..98e9aed 100644
--- a/diff.h
+++ b/diff.h
@@ -124,6 +124,7 @@ struct diff_options {
 
 	int stat_width;
 	int stat_name_width;
+	int stat_lines;
 	const char *word_regex;
 	enum diff_words_type word_diff;
 
-- 
1.7.5.250.g4493b