builtin-notes: Add "prune" subcommand for removing notes for missing objects

"git notes prune" will remove all notes that annotate unreachable/non-
existing objects.

The patch includes tests verifying correct behaviour of the new subcommand.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-notes.txt

@@ -8,7 +8,7 @@ git-notes - Add/inspect commit notes
 SYNOPSIS
 --------
 [verse]
-'git notes' (edit [-F <file> | -m <msg>] | show | remove) [commit]
+'git notes' (edit [-F <file> | -m <msg>] | show | remove | prune) [commit]
 
 DESCRIPTION
 -----------
@@ -37,6 +37,8 @@ remove::
 	This is equivalent to specifying an empty note message to
 	the `edit` subcommand.
 
+prune::
+	Remove all notes for non-existing/unreachable objects.
 
 OPTIONS
 -------

builtin-notes.c

@@ -21,6 +21,7 @@ static const char * const git_notes_usage[] = {
 	"git notes edit [-m <msg> | -F <file>] [<object>]",
 	"git notes show [<object>]",
 	"git notes remove [<object>]",
+	"git notes prune",
 	NULL
 };
 
@@ -201,7 +202,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 	const char *object_ref;
 	char logmsg[100];
 
-	int edit = 0, show = 0, remove = 0;
+	int edit = 0, show = 0, remove = 0, prune = 0;
 	const char *msgfile = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
 	struct option options[] = {
@@ -222,8 +223,10 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		show = 1;
 	else if (argc && !strcmp(argv[0], "remove"))
 		remove = 1;
+	else if (argc && !strcmp(argv[0], "prune"))
+		prune = 1;
 
-	if (edit + show + remove != 1)
+	if (edit + show + remove + prune != 1)
 		usage_with_options(git_notes_usage, options);
 
 	if ((msg.given || msgfile) && !edit) {
@@ -237,7 +240,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 	}
 
 	object_ref = argc == 2 ? argv[1] : "HEAD";
-	if (argc > 2) {
+	if (argc > 2 || (prune && argc > 1)) {
 		error("too many parameters");
 		usage_with_options(git_notes_usage, options);
 	}
@@ -264,7 +267,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		return execv_git_cmd(show_args);
 	}
 
-	/* edit/remove command */
+	/* edit/remove/prune command */
 
 	if (remove)
 		strbuf_reset(&buf);
@@ -278,12 +281,17 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 			die_errno("could not open or read '%s'", msgfile);
 	}
 
-	create_note(object, &buf, msg.given || msgfile || remove, note,
-		    new_note);
-	if (is_null_sha1(new_note))
-		remove_note(t, object);
-	else
-		add_note(t, object, new_note, combine_notes_overwrite);
+	if (prune) {
+		hashclr(new_note);
+		prune_notes(t);
+	} else {
+		create_note(object, &buf, msg.given || msgfile || remove, note,
+			    new_note);
+		if (is_null_sha1(new_note))
+			remove_note(t, object);
+		else
+			add_note(t, object, new_note, combine_notes_overwrite);
+	}
 	snprintf(logmsg, sizeof(logmsg), "Note %s by 'git notes %s'",
 		 is_null_sha1(new_note) ? "removed" : "added", argv[0]);
 	commit_notes(t, logmsg);

t/t3306-notes-prune.sh

@@ -0,0 +1,94 @@
+#!/bin/sh
+
+test_description='Test git notes prune'
+
+. ./test-lib.sh
+
+test_expect_success 'setup: create a few commits with notes' '
+
+	: > file1 &&
+	git add file1 &&
+	test_tick &&
+	git commit -m 1st &&
+	git notes edit -m "Note #1" &&
+	: > file2 &&
+	git add file2 &&
+	test_tick &&
+	git commit -m 2nd &&
+	git notes edit -m "Note #2" &&
+	: > file3 &&
+	git add file3 &&
+	test_tick &&
+	git commit -m 3rd &&
+	git notes edit -m "Note #3"
+'
+
+cat > expect <<END_OF_LOG
+commit 5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:15:13 2005 -0700
+
+    3rd
+
+Notes:
+    Note #3
+
+commit 08341ad9e94faa089d60fd3f523affb25c6da189
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:14:13 2005 -0700
+
+    2nd
+
+Notes:
+    Note #2
+
+commit ab5f302035f2e7aaf04265f08b42034c23256e1f
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:13:13 2005 -0700
+
+    1st
+
+Notes:
+    Note #1
+END_OF_LOG
+
+test_expect_success 'verify commits and notes' '
+
+	git log > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'remove some commits' '
+
+	git reset --hard HEAD~2 &&
+	git reflog expire --expire=now HEAD &&
+	git gc --prune=now
+'
+
+test_expect_success 'verify that commits are gone' '
+
+	! git cat-file -p 5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29 &&
+	! git cat-file -p 08341ad9e94faa089d60fd3f523affb25c6da189 &&
+	git cat-file -p ab5f302035f2e7aaf04265f08b42034c23256e1f
+'
+
+test_expect_success 'verify that notes are still present' '
+
+	git notes show 5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29 &&
+	git notes show 08341ad9e94faa089d60fd3f523affb25c6da189 &&
+	git notes show ab5f302035f2e7aaf04265f08b42034c23256e1f
+'
+
+test_expect_success 'prune notes' '
+
+	git notes prune
+'
+
+test_expect_success 'verify that notes are gone' '
+
+	! git notes show 5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29 &&
+	! git notes show 08341ad9e94faa089d60fd3f523affb25c6da189 &&
+	git notes show ab5f302035f2e7aaf04265f08b42034c23256e1f
+'
+
+test_done