notes: dry-run and verbose options for prune

Introduce -n and -v options for "git notes prune" in complete analogy to
"git prune" so that one can check for dangling notes easily.

The output is a list of names of objects whose notes would be resp.
are removed so that one can check the object ("git show sha1") as well as
the note ("git notes show sha1").

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Acked-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-notes.txt

@@ -15,7 +15,7 @@ SYNOPSIS
 'git notes' edit [<object>]
 'git notes' show [<object>]
 'git notes' remove [<object>]
-'git notes' prune
+'git notes' prune [-n | -v]
 
 
 DESCRIPTION
@@ -121,6 +121,13 @@ OPTIONS
 	GIT_NOTES_REF and the "core.notesRef" configuration.  The ref
 	is taken to be in `refs/notes/` if it is not qualified.
 
+-n::
+	Do not remove anything; just report the object names whose notes
+	would be removed.
+
+-v::
+	Report all object names whose notes are removed.
+
 
 NOTES
 -----

builtin/notes.c

@@ -26,7 +26,7 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
 	"git notes [--ref <notes_ref>] remove [<object>]",
-	"git notes [--ref <notes_ref>] prune",
+	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
 };
 
@@ -67,7 +67,7 @@ static const char * const git_notes_remove_usage[] = {
 };
 
 static const char * const git_notes_prune_usage[] = {
-	"git notes prune",
+	"git notes prune [<options>]",
 	NULL
 };
 
@@ -792,7 +792,10 @@ static int remove_cmd(int argc, const char **argv, const char *prefix)
 static int prune(int argc, const char **argv, const char *prefix)
 {
 	struct notes_tree *t;
+	int show_only = 0, verbose = 0;
 	struct option options[] = {
+		OPT_BOOLEAN('n', NULL, &show_only, "do not remove, show only"),
+		OPT_BOOLEAN('v', NULL, &verbose, "report pruned notes"),
 		OPT_END()
 	};
 
@@ -806,8 +809,10 @@ static int prune(int argc, const char **argv, const char *prefix)
 
 	t = init_notes_check("prune");
 
-	prune_notes(t);
-	commit_notes(t, "Notes removed by 'git notes prune'");
+	prune_notes(t, (verbose ? NOTES_PRUNE_VERBOSE : 0) |
+		(show_only ? NOTES_PRUNE_VERBOSE|NOTES_PRUNE_DRYRUN : 0) );
+	if (!show_only)
+		commit_notes(t, "Notes removed by 'git notes prune'");
 	free_notes(t);
 	return 0;
 }

notes.c

@@ -1083,7 +1083,7 @@ int write_notes_tree(struct notes_tree *t, unsigned char *result)
 	return ret;
 }
 
-void prune_notes(struct notes_tree *t)
+void prune_notes(struct notes_tree *t, int flags)
 {
 	struct note_delete_list *l = NULL;
 
@@ -1094,7 +1094,10 @@ void prune_notes(struct notes_tree *t)
 	for_each_note(t, 0, prune_notes_helper, &l);
 
 	while (l) {
-		remove_note(t, l->sha1);
+		if (flags & NOTES_PRUNE_VERBOSE)
+			printf("%s\n", sha1_to_hex(l->sha1));
+		if (!(flags & NOTES_PRUNE_DRYRUN))
+			remove_note(t, l->sha1);
 		l = l->next;
 	}
 }

notes.h

@@ -171,6 +171,9 @@ int for_each_note(struct notes_tree *t, int flags, each_note_fn fn,
  */
 int write_notes_tree(struct notes_tree *t, unsigned char *result);
 
+/* Flags controlling the operation of prune */
+#define NOTES_PRUNE_VERBOSE 1
+#define NOTES_PRUNE_DRYRUN 2
 /*
  * Remove all notes annotating non-existing objects from the given notes tree
  *
@@ -181,7 +184,7 @@ int write_notes_tree(struct notes_tree *t, unsigned char *result);
  * structure are not persistent until a subsequent call to write_notes_tree()
  * returns zero.
  */
-void prune_notes(struct notes_tree *t);
+void prune_notes(struct notes_tree *t, int flags);
 
 /*
  * Free (and de-initialize) the given notes_tree structure

t/t3306-notes-prune.sh

@@ -60,15 +60,15 @@ test_expect_success 'verify commits and notes' '
 
 test_expect_success 'remove some commits' '
 
-	git reset --hard HEAD~2 &&
+	git reset --hard HEAD~1 &&
 	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 08341ad9e94faa089d60fd3f523affb25c6da189 &&
 	git cat-file -p ab5f302035f2e7aaf04265f08b42034c23256e1f
 '
 
@@ -79,11 +79,55 @@ test_expect_success 'verify that notes are still present' '
 	git notes show ab5f302035f2e7aaf04265f08b42034c23256e1f
 '
 
+test_expect_success 'prune -n does not remove notes' '
+
+	git notes list > expect &&
+	git notes prune -n &&
+	git notes list > actual &&
+	test_cmp expect actual
+'
+
+cat > expect <<EOF
+5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29
+EOF
+
+test_expect_success 'prune -n lists prunable notes' '
+
+
+	git notes prune -n > actual &&
+	test_cmp expect actual
+'
+
+
 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_expect_success 'remove some commits' '
+
+	git reset --hard HEAD~1 &&
+	git reflog expire --expire=now HEAD &&
+	git gc --prune=now
+'
+
+cat > expect <<EOF
+08341ad9e94faa089d60fd3f523affb25c6da189
+EOF
+
+test_expect_success 'prune -v notes' '
+
+	git notes prune -v > actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'verify that notes are gone' '
 
 	! git notes show 5ee1c35e83ea47cd3cc4f8cbee0568915fbbbd29 &&