range-diff: treat notes like `log`

Currently, `range-diff` shows the default notes if no notes-related
arguments are given. This is also how `log` behaves. But unlike
`range-diff`, `log` does *not* show the default notes if
`--notes=<custom>` are given. In other words, this:

    git log --notes=custom

is equivalent to this:

    git log --no-notes --notes=custom

While:

    git range-diff --notes=custom

acts like this:

    git log --notes --notes-custom

This can’t be how the user expects `range-diff` to behave given that the
man page for `range-diff` under `--[no-]notes[=<ref>]` says:

> This flag is passed to the `git log` program (see git-log(1)) that
> generates the patches.

This behavior also affects `format-patch` since it uses `range-diff` for
the cover letter. Unlike `log`, though, `format-patch` is not supposed
to show the default notes if no notes-related arguments are given.[1]
But this promise is broken when the range-diff happens to have something
to say about the changes to the default notes, since that will be shown
in the cover letter.

Remedy this by introducing `--show-notes-by-default` that `range-diff` can
use to tell the `log` subprocess what to do.

§ Authors

• Fix by Johannes
• Tests by Kristoffer

† 1: See e.g. 66b2ed09c2 (Fix "log" family not to be too agressive about
    showing notes, 2010-01-20).

Co-authored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/pretty-options.txt

@@ -87,6 +87,10 @@ being displayed. Examples: "--notes=foo" will show only notes from
 	"--notes --notes=foo --no-notes --notes=bar" will only show notes
 	from "refs/notes/bar".
 
+--show-notes-by-default::
+	Show the default notes unless options for displaying specific
+	notes are given.
+
 --show-notes[=<ref>]::
 --[no-]standard-notes::
 	These options are deprecated. Use the above --notes/--no-notes

range-diff.c

@@ -60,7 +60,7 @@ static int read_patches(const char *range, struct string_list *list,
 		     "--output-indicator-context=#",
 		     "--no-abbrev-commit",
 		     "--pretty=medium",
-		     "--notes",
+		     "--show-notes-by-default",
 		     NULL);
 	strvec_push(&cp.args, range);
 	if (other_arg)

revision.c

@@ -2484,6 +2484,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->break_bar = xstrdup(optarg);
 		revs->track_linear = 1;
 		revs->track_first_time = 1;
+	} else if (!strcmp(arg, "--show-notes-by-default")) {
+		revs->show_notes_by_default = 1;
 	} else if (skip_prefix(arg, "--show-notes=", &optarg) ||
 		   skip_prefix(arg, "--notes=", &optarg)) {
 		if (starts_with(arg, "--show-notes=") &&
@@ -3054,6 +3056,11 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (revs->expand_tabs_in_log < 0)
 		revs->expand_tabs_in_log = revs->expand_tabs_in_log_default;
 
+	if (!revs->show_notes_given && revs->show_notes_by_default) {
+		enable_default_display_notes(&revs->notes_opt, &revs->show_notes);
+		revs->show_notes_given = 1;
+	}
+
 	return left;
 }
 

revision.h

@@ -253,6 +253,7 @@ struct rev_info {
 			shown_dashes:1,
 			show_merge:1,
 			show_notes_given:1,
+			show_notes_by_default:1,
 			show_signature:1,
 			pretty_given:1,
 			abbrev_commit:1,

t/t3206-range-diff.sh

@@ -662,6 +662,20 @@ test_expect_success 'range-diff with multiple --notes' '
 	test_cmp expect actual
 '
 
+# `range-diff` should act like `log` with regards to notes
+test_expect_success 'range-diff with --notes=custom does not show default notes' '
+	git notes add -m "topic note" topic &&
+	git notes add -m "unmodified note" unmodified &&
+	git notes --ref=custom add -m "topic note" topic &&
+	git notes --ref=custom add -m "unmodified note" unmodified &&
+	test_when_finished git notes remove topic unmodified &&
+	test_when_finished git notes --ref=custom remove topic unmodified &&
+	git range-diff --notes=custom main..topic main..unmodified \
+		>actual &&
+	! grep "## Notes ##" actual &&
+	grep "## Notes (custom) ##" actual
+'
+
 test_expect_success 'format-patch --range-diff does not compare notes by default' '
 	git notes add -m "topic note" topic &&
 	git notes add -m "unmodified note" unmodified &&
@@ -679,6 +693,20 @@ test_expect_success 'format-patch --range-diff does not compare notes by default
 	! grep "note" 0000-*
 '
 
+test_expect_success 'format-patch --notes=custom --range-diff only compares custom notes' '
+	git notes add -m "topic note" topic &&
+	git notes --ref=custom add -m "topic note (custom)" topic &&
+	git notes add -m "unmodified note" unmodified &&
+	git notes --ref=custom add -m "unmodified note (custom)" unmodified &&
+	test_when_finished git notes remove topic unmodified &&
+	test_when_finished git notes --ref=custom remove topic unmodified &&
+	git format-patch --notes=custom --cover-letter --range-diff=$prev \
+		main..unmodified >actual &&
+	test_when_finished "rm 000?-*" &&
+	grep "## Notes (custom) ##" 0000-* &&
+	! grep "## Notes ##" 0000-*
+'
+
 test_expect_success 'format-patch --range-diff with --no-notes' '
 	git notes add -m "topic note" topic &&
 	git notes add -m "unmodified note" unmodified &&