notes: implement 'git notes copy --stdin'

This implements a mass-copy command that takes a sequence of lines in
the format

  <from-sha1> SP <to-sha1> [ SP <rest> ] LF

on stdin, and copies each <from-sha1>'s notes to the <to-sha1>.  The
<rest> is ignored.  The intent, of course, is that this can read the
same input that the 'post-rewrite' hook gets.

The copy_note() function is exposed for everyone's and in particular
the next commit's use.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Acked-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-notes.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 [verse]
 'git notes' [list [<object>]]
 'git notes' add [-f] [-F <file> | -m <msg> | (-c | -C) <object>] [<object>]
-'git notes' copy [-f] <from-object> <to-object>
+'git notes' copy [-f] ( --stdin | <from-object> <to-object> )
 'git notes' append [-F <file> | -m <msg> | (-c | -C) <object>] [<object>]
 'git notes' edit [<object>]
 'git notes' show [<object>]
@@ -56,6 +56,16 @@ copy::
 	objects has none. (use -f to overwrite existing notes to the
 	second object). This subcommand is equivalent to:
 	`git notes add [-f] -C $(git notes list <from-object>) <to-object>`
++
+In `\--stdin` mode, take lines in the format
++
+----------
+<from-object> SP <to-object> [ SP <rest> ] LF
+----------
++
+on standard input, and copy the notes from each <from-object> to its
+corresponding <to-object>.  (The optional `<rest>` is ignored so that
+the command can read the input given to the `post-rewrite` hook.)
 
 append::
 	Append to the notes of an existing object (defaults to HEAD).

builtin-notes.c

@@ -278,6 +278,46 @@ int commit_notes(struct notes_tree *t, const char *msg)
 	return 0;
 }
 
+int notes_copy_from_stdin(int force)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct notes_tree *t;
+	int ret = 0;
+
+	init_notes(NULL, NULL, NULL, 0);
+	t = &default_notes_tree;
+
+	while (strbuf_getline(&buf, stdin, '\n') != EOF) {
+		unsigned char from_obj[20], to_obj[20];
+		struct strbuf **split;
+		int err;
+
+		split = strbuf_split(&buf, ' ');
+		if (!split[0] || !split[1])
+			die("Malformed input line: '%s'.", buf.buf);
+		strbuf_rtrim(split[0]);
+		strbuf_rtrim(split[1]);
+		if (get_sha1(split[0]->buf, from_obj))
+			die("Failed to resolve '%s' as a valid ref.", split[0]->buf);
+		if (get_sha1(split[1]->buf, to_obj))
+			die("Failed to resolve '%s' as a valid ref.", split[1]->buf);
+
+		err = copy_note(t, from_obj, to_obj, force, combine_notes_overwrite);
+
+		if (err) {
+			error("Failed to copy notes from '%s' to '%s'",
+			      split[0]->buf, split[1]->buf);
+			ret = 1;
+		}
+
+		strbuf_list_free(split);
+	}
+
+	commit_notes(t, "Notes added by 'git notes copy'");
+	free_notes(t);
+	return ret;
+}
+
 int cmd_notes(int argc, const char **argv, const char *prefix)
 {
 	struct notes_tree *t;
@@ -287,7 +327,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 	char logmsg[100];
 
 	int list = 0, add = 0, copy = 0, append = 0, edit = 0, show = 0,
-	    remove = 0, prune = 0, force = 0;
+	    remove = 0, prune = 0, force = 0, from_stdin = 0;
 	int given_object = 0, i = 1, retval = 0;
 	struct msg_arg msg = { 0, 0, STRBUF_INIT };
 	struct option options[] = {
@@ -301,6 +341,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		OPT_CALLBACK('C', "reuse-message", &msg, "OBJECT",
 			   "reuse specified note object", parse_reuse_arg),
 		OPT_BOOLEAN('f', "force", &force, "replace existing notes"),
+		OPT_BOOLEAN(0, "stdin", &from_stdin, "read objects from stdin"),
 		OPT_END()
 	};
 
@@ -349,8 +390,21 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		usage_with_options(git_notes_usage, options);
 	}
 
+	if (!copy && from_stdin) {
+		error("cannot use --stdin with %s subcommand.", argv[0]);
+		usage_with_options(git_notes_usage, options);
+	}
+
 	if (copy) {
 		const char *from_ref;
+		if (from_stdin) {
+			if (argc > 1) {
+				error("too many parameters");
+				usage_with_options(git_notes_usage, options);
+			} else {
+				return notes_copy_from_stdin(force);
+			}
+		}
 		if (argc < 3) {
 			error("too few parameters");
 			usage_with_options(git_notes_usage, options);

notes.c

@@ -1185,3 +1185,21 @@ void format_display_notes(const unsigned char *object_sha1,
 		format_note(display_notes_trees[i], object_sha1, sb,
 			    output_encoding, flags);
 }
+
+int copy_note(struct notes_tree *t,
+	      const unsigned char *from_obj, const unsigned char *to_obj,
+	      int force, combine_notes_fn combine_fn)
+{
+	const unsigned char *note = get_note(t, from_obj);
+	const unsigned char *existing_note = get_note(t, to_obj);
+
+	if (!force && existing_note)
+		return 1;
+
+	if (note)
+		add_note(t, to_obj, note, combine_fn);
+	else if (existing_note)
+		add_note(t, to_obj, null_sha1, combine_fn);
+
+	return 0;
+}

notes.h

@@ -99,6 +99,15 @@ void remove_note(struct notes_tree *t, const unsigned char *object_sha1);
 const unsigned char *get_note(struct notes_tree *t,
 		const unsigned char *object_sha1);
 
+/*
+ * Copy a note from one object to another in the given notes_tree.
+ *
+ * Fails if the to_obj already has a note unless 'force' is true.
+ */
+int copy_note(struct notes_tree *t,
+	      const unsigned char *from_obj, const unsigned char *to_obj,
+	      int force, combine_notes_fn combine_fn);
+
 /*
  * Flags controlling behaviour of for_each_note()
  *

t/t3301-notes.sh

@@ -776,4 +776,38 @@ test_expect_success 'cannot copy note from object without notes' '
 	test_must_fail git notes copy HEAD^ HEAD
 '
 
+cat > expect << EOF
+commit e5d4fb5698d564ab8c73551538ecaf2b0c666185
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:25:13 2005 -0700
+
+    13th
+
+Notes (other):
+    yet another note
+$whitespace
+    yet another note
+
+commit 7038787dfe22a14c3867ce816dbba39845359719
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:24:13 2005 -0700
+
+    12th
+
+Notes (other):
+    other note
+$whitespace
+    yet another note
+EOF
+
+test_expect_success 'git notes copy --stdin' '
+	(echo $(git rev-parse HEAD~3) $(git rev-parse HEAD^); \
+	echo $(git rev-parse HEAD~2) $(git rev-parse HEAD)) |
+	git notes copy --stdin &&
+	git log -2 > output &&
+	test_cmp expect output &&
+	test "$(git notes list HEAD)" = "$(git notes list HEAD~2)" &&
+	test "$(git notes list HEAD^)" = "$(git notes list HEAD~3)"
+'
+
 test_done