diff: add --compact-summary

Certain information is currently shown with --summary, but when used
in combination with --stat it's a bit hard to read since info of the
same file is in two places (--stat and --summary).

On top of that, commits that add or remove files double the number of
display lines, which could be a lot if you add or remove a lot of
files.

--compact-summary embeds most of --summary back in --stat in the
little space between the file name part and the graph line, e.g. with
commit 0433d533f1:

   Documentation/merge-config.txt         |  4 +
   builtin/merge.c                        |  2 +
   ...-pull-verify-signatures.sh (new +x) | 81 ++++++++++++++
   t/t7612-merge-verify-signatures.sh     | 45 ++++++++
   4 files changed, 132 insertions(+)

It helps both condensing information and saving some text
space. What's new in diffstat is:

- A new 0644 file is shown as (new)
- A new 0755 file is shown as (new +x)
- A new symlink is shown as (new +l)
- A deleted file is shown as (gone)
- A mode change adding executable bit is shown as (mode +x)
- A mode change removing it is shown as (mode -x)

Note that --compact-summary does not contain all the information
--summary provides. Rewrite percentage is not shown but it could be
added later, like R50% or C20%.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/diff.c b/diff.c
index c0b75de..95124c0 100644
--- a/diff.c
+++ b/diff.c
@@ -2129,6 +2129,7 @@ struct diffstat_t {
 		char *from_name;
 		char *name;
 		char *print_name;
+		const char *comments;
 		unsigned is_unmerged:1;
 		unsigned is_binary:1;
 		unsigned is_renamed:1;
@@ -2205,6 +2206,9 @@ static void fill_print_name(struct diffstat_file *file)
 	else
 		quote_c_style(file->name, &pname, NULL, 0);
 
+	if (file->comments)
+		strbuf_addf(&pname, " (%s)", file->comments);
+
 	file->print_name = strbuf_detach(&pname, NULL);
 }
 
@@ -3239,6 +3243,32 @@ static void builtin_diff(const char *name_a,
 	return;
 }
 
+static char *get_compact_summary(const struct diff_filepair *p, int is_renamed)
+{
+	if (!is_renamed) {
+		if (p->status == DIFF_STATUS_ADDED) {
+			if (S_ISLNK(p->two->mode))
+				return "new +l";
+			else if ((p->two->mode & 0777) == 0755)
+				return "new +x";
+			else
+				return "new";
+		} else if (p->status == DIFF_STATUS_DELETED)
+			return "gone";
+	}
+	if (S_ISLNK(p->one->mode) && !S_ISLNK(p->two->mode))
+		return "mode -l";
+	else if (!S_ISLNK(p->one->mode) && S_ISLNK(p->two->mode))
+		return "mode +l";
+	else if ((p->one->mode & 0777) == 0644 &&
+		 (p->two->mode & 0777) == 0755)
+		return "mode +x";
+	else if ((p->one->mode & 0777) == 0755 &&
+		 (p->two->mode & 0777) == 0644)
+		return "mode -x";
+	return NULL;
+}
+
 static void builtin_diffstat(const char *name_a, const char *name_b,
 			     struct diff_filespec *one,
 			     struct diff_filespec *two,
@@ -3258,6 +3288,8 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 
 	data = diffstat_add(diffstat, name_a, name_b);
 	data->is_interesting = p->status != DIFF_STATUS_UNKNOWN;
+	if (o->flags.stat_with_summary)
+		data->comments = get_compact_summary(p, data->is_renamed);
 
 	if (!one || !two) {
 		data->is_unmerged = 1;
@@ -4528,6 +4560,11 @@ int diff_opt_parse(struct diff_options *options,
 	else if (starts_with(arg, "--stat"))
 		/* --stat, --stat-width, --stat-name-width, or --stat-count */
 		return stat_opt(options, av);
+	else if (!strcmp(arg, "--compact-summary")) {
+		 options->flags.stat_with_summary = 1;
+		 options->output_format |= DIFF_FORMAT_DIFFSTAT;
+	} else if (!strcmp(arg, "--no-compact-summary"))
+		 options->flags.stat_with_summary = 0;
 
 	/* renames options */
 	else if (starts_with(arg, "-B") ||