Merge branch 'mh/notes-allow-reading-treeish'

Some "git notes" operations, e.g. "git log --notes=<note>", should
be able to read notes from any tree-ish that is shaped like a notes
tree, but the notes infrastructure required that the argument must
be a ref under refs/notes/.  Loosen it to require a valid ref only
when the operation would update the notes (in which case we must
have a place to store the updated notes tree, iow, a ref).

* mh/notes-allow-reading-treeish:
  notes: allow treeish expressions as notes ref

Documentation/pretty-options.txt

@@ -43,7 +43,7 @@ people using 80-column terminals.
 	commit may be copied to the output.
 
 ifndef::git-rev-list[]
---notes[=<ref>]::
+--notes[=<treeish>]::
 	Show the notes (see linkgit:git-notes[1]) that annotate the
 	commit, when showing the commit log message.  This is the default
 	for `git log`, `git show` and `git whatchanged` commands when
@@ -54,8 +54,8 @@ By default, the notes shown are from the notes refs listed in the
 'core.notesRef' and 'notes.displayRef' variables (or corresponding
 environment overrides). See linkgit:git-config[1] for more details.
 +
-With an optional '<ref>' argument, show this notes ref instead of the
-default notes ref(s). The ref specifies the full refname when it begins
+With an optional '<treeish>' argument, use the treeish to find the notes
+to display.  The treeish can specify the full refname when it begins
 with `refs/notes/`; when it begins with `notes/`, `refs/` and otherwise
 `refs/notes/` is prefixed to form a full name of the ref.
 +
@@ -71,7 +71,7 @@ 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[=<ref>]::
+--show-notes[=<treeish>]::
 --[no-]standard-notes::
 	These options are deprecated. Use the above --notes/--no-notes
 	options instead.

builtin/notes.c

@@ -286,7 +286,7 @@ static int notes_copy_from_stdin(int force, const char *rewrite_cmd)
 		if (!c)
 			return 0;
 	} else {
-		init_notes(NULL, NULL, NULL, 0);
+		init_notes(NULL, NULL, NULL, NOTES_INIT_WRITABLE);
 		t = &default_notes_tree;
 	}
 
@@ -329,15 +329,18 @@ static int notes_copy_from_stdin(int force, const char *rewrite_cmd)
 	return ret;
 }
 
-static struct notes_tree *init_notes_check(const char *subcommand)
+static struct notes_tree *init_notes_check(const char *subcommand,
+					   int flags)
 {
 	struct notes_tree *t;
-	init_notes(NULL, NULL, NULL, 0);
+	const char *ref;
+	init_notes(NULL, NULL, NULL, flags);
 	t = &default_notes_tree;
 
-	if (!starts_with(t->ref, "refs/notes/"))
+	ref = (flags & NOTES_INIT_WRITABLE) ? t->update_ref : t->ref;
+	if (!starts_with(ref, "refs/notes/"))
 		die("Refusing to %s notes in %s (outside of refs/notes/)",
-		    subcommand, t->ref);
+		    subcommand, ref);
 	return t;
 }
 
@@ -360,7 +363,7 @@ static int list(int argc, const char **argv, const char *prefix)
 		usage_with_options(git_notes_list_usage, options);
 	}
 
-	t = init_notes_check("list");
+	t = init_notes_check("list", 0);
 	if (argc) {
 		if (get_sha1(argv[0], object))
 			die(_("Failed to resolve '%s' as a valid ref."), argv[0]);
@@ -420,7 +423,7 @@ static int add(int argc, const char **argv, const char *prefix)
 	if (get_sha1(object_ref, object))
 		die(_("Failed to resolve '%s' as a valid ref."), object_ref);
 
-	t = init_notes_check("add");
+	t = init_notes_check("add", NOTES_INIT_WRITABLE);
 	note = get_note(t, object);
 
 	if (note) {
@@ -511,7 +514,7 @@ static int copy(int argc, const char **argv, const char *prefix)
 	if (get_sha1(object_ref, object))
 		die(_("Failed to resolve '%s' as a valid ref."), object_ref);
 
-	t = init_notes_check("copy");
+	t = init_notes_check("copy", NOTES_INIT_WRITABLE);
 	note = get_note(t, object);
 
 	if (note) {
@@ -589,7 +592,7 @@ static int append_edit(int argc, const char **argv, const char *prefix)
 	if (get_sha1(object_ref, object))
 		die(_("Failed to resolve '%s' as a valid ref."), object_ref);
 
-	t = init_notes_check(argv[0]);
+	t = init_notes_check(argv[0], NOTES_INIT_WRITABLE);
 	note = get_note(t, object);
 
 	prepare_note_data(object, &d, edit ? note : NULL);
@@ -652,7 +655,7 @@ static int show(int argc, const char **argv, const char *prefix)
 	if (get_sha1(object_ref, object))
 		die(_("Failed to resolve '%s' as a valid ref."), object_ref);
 
-	t = init_notes_check("show");
+	t = init_notes_check("show", 0);
 	note = get_note(t, object);
 
 	if (!note)
@@ -809,7 +812,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 	expand_notes_ref(&remote_ref);
 	o.remote_ref = remote_ref.buf;
 
-	t = init_notes_check("merge");
+	t = init_notes_check("merge", NOTES_INIT_WRITABLE);
 
 	if (strategy) {
 		if (parse_notes_merge_strategy(strategy, &o.strategy)) {
@@ -901,7 +904,7 @@ static int remove_cmd(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options,
 			     git_notes_remove_usage, 0);
 
-	t = init_notes_check("remove");
+	t = init_notes_check("remove", NOTES_INIT_WRITABLE);
 
 	if (!argc && !from_stdin) {
 		retval = remove_one_note(t, "HEAD", flag);
@@ -943,7 +946,7 @@ static int prune(int argc, const char **argv, const char *prefix)
 		usage_with_options(git_notes_prune_usage, options);
 	}
 
-	t = init_notes_check("prune");
+	t = init_notes_check("prune", NOTES_INIT_WRITABLE);
 
 	prune_notes(t, (verbose ? NOTES_PRUNE_VERBOSE : 0) |
 		(show_only ? NOTES_PRUNE_VERBOSE|NOTES_PRUNE_DRYRUN : 0) );

notes-cache.c

@@ -32,14 +32,14 @@ void notes_cache_init(struct notes_cache *c, const char *name,
 		     const char *validity)
 {
 	struct strbuf ref = STRBUF_INIT;
-	int flags = 0;
+	int flags = NOTES_INIT_WRITABLE;
 
 	memset(c, 0, sizeof(*c));
 	c->validity = xstrdup(validity);
 
 	strbuf_addf(&ref, "refs/notes/%s", name);
 	if (!notes_cache_match_validity(ref.buf, validity))
-		flags = NOTES_INIT_EMPTY;
+		flags |= NOTES_INIT_EMPTY;
 	init_notes(&c->tree, ref.buf, combine_notes_overwrite, flags);
 	strbuf_release(&ref);
 }
@@ -49,7 +49,8 @@ int notes_cache_write(struct notes_cache *c)
 	unsigned char tree_sha1[20];
 	unsigned char commit_sha1[20];
 
-	if (!c || !c->tree.initialized || !c->tree.ref || !*c->tree.ref)
+	if (!c || !c->tree.initialized || !c->tree.update_ref ||
+	    !*c->tree.update_ref)
 		return -1;
 	if (!c->tree.dirty)
 		return 0;
@@ -59,8 +60,8 @@ int notes_cache_write(struct notes_cache *c)
 	if (commit_tree(c->validity, strlen(c->validity), tree_sha1, NULL,
 			commit_sha1, NULL, NULL) < 0)
 		return -1;
-	if (update_ref("update notes cache", c->tree.ref, commit_sha1, NULL,
-		       0, UPDATE_REFS_QUIET_ON_ERR) < 0)
+	if (update_ref("update notes cache", c->tree.update_ref, commit_sha1,
+		       NULL, 0, UPDATE_REFS_QUIET_ON_ERR) < 0)
 		return -1;
 
 	return 0;

notes-utils.c

@@ -37,7 +37,7 @@ void commit_notes(struct notes_tree *t, const char *msg)
 
 	if (!t)
 		t = &default_notes_tree;
-	if (!t->initialized || !t->ref || !*t->ref)
+	if (!t->initialized || !t->update_ref || !*t->update_ref)
 		die(_("Cannot commit uninitialized/unreferenced notes tree"));
 	if (!t->dirty)
 		return; /* don't have to commit an unchanged tree */
@@ -48,7 +48,7 @@ void commit_notes(struct notes_tree *t, const char *msg)
 
 	create_notes_commit(t, NULL, buf.buf, buf.len, commit_sha1);
 	strbuf_insert(&buf, 0, "notes: ", 7); /* commit message starts at index 7 */
-	update_ref(buf.buf, t->ref, commit_sha1, NULL, 0,
+	update_ref(buf.buf, t->update_ref, commit_sha1, NULL, 0,
 		   UPDATE_REFS_DIE_ON_ERR);
 
 	strbuf_release(&buf);
@@ -148,7 +148,7 @@ struct notes_rewrite_cfg *init_copy_notes_for_rewrite(const char *cmd)
 		free(c);
 		return NULL;
 	}
-	c->trees = load_notes_trees(c->refs);
+	c->trees = load_notes_trees(c->refs, NOTES_INIT_WRITABLE);
 	string_list_clear(c->refs, 0);
 	free(c->refs);
 	return c;

notes.c

@@ -1011,13 +1011,16 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 	t->first_non_note = NULL;
 	t->prev_non_note = NULL;
 	t->ref = xstrdup_or_null(notes_ref);
+	t->update_ref = (flags & NOTES_INIT_WRITABLE) ? t->ref : NULL;
 	t->combine_notes = combine_notes;
 	t->initialized = 1;
 	t->dirty = 0;
 
 	if (flags & NOTES_INIT_EMPTY || !notes_ref ||
-	    read_ref(notes_ref, object_sha1))
+	    get_sha1_treeish(notes_ref, object_sha1))
 		return;
+	if (flags & NOTES_INIT_WRITABLE && read_ref(notes_ref, object_sha1))
+		die("Cannot use notes ref %s", notes_ref);
 	if (get_tree_entry(object_sha1, "", sha1, &mode))
 		die("Failed to read notes tree referenced by %s (%s)",
 		    notes_ref, sha1_to_hex(object_sha1));
@@ -1027,7 +1030,7 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 	load_subtree(t, &root_tree, t->root, 0);
 }
 
-struct notes_tree **load_notes_trees(struct string_list *refs)
+struct notes_tree **load_notes_trees(struct string_list *refs, int flags)
 {
 	struct string_list_item *item;
 	int counter = 0;
@@ -1035,7 +1038,7 @@ struct notes_tree **load_notes_trees(struct string_list *refs)
 	trees = xmalloc((refs->nr+1) * sizeof(struct notes_tree *));
 	for_each_string_list_item(item, refs) {
 		struct notes_tree *t = xcalloc(1, sizeof(struct notes_tree));
-		init_notes(t, item->string, combine_notes_ignore, 0);
+		init_notes(t, item->string, combine_notes_ignore, flags);
 		trees[counter++] = t;
 	}
 	trees[counter] = NULL;
@@ -1071,7 +1074,7 @@ void init_display_notes(struct display_notes_opt *opt)
 						     item->string);
 	}
 
-	display_notes_trees = load_notes_trees(&display_notes_refs);
+	display_notes_trees = load_notes_trees(&display_notes_refs, 0);
 	string_list_clear(&display_notes_refs, 0);
 }
 

notes.h

@@ -44,6 +44,7 @@ extern struct notes_tree {
 	struct int_node *root;
 	struct non_note *first_non_note, *prev_non_note;
 	char *ref;
+	char *update_ref;
 	combine_notes_fn combine_notes;
 	int initialized;
 	int dirty;
@@ -71,6 +72,13 @@ const char *default_notes_ref(void);
  */
 #define NOTES_INIT_EMPTY 1
 
+/*
+ * By default, the notes tree is only readable, and the notes ref can be
+ * any treeish. The notes tree can however be made writable with this flag,
+ * in which case only strict ref names can be used.
+ */
+#define NOTES_INIT_WRITABLE 2
+
 /*
  * Initialize the given notes_tree with the notes tree structure at the given
  * ref. If given ref is NULL, the value of the $GIT_NOTES_REF environment
@@ -276,7 +284,7 @@ void format_display_notes(const unsigned char *object_sha1,
  * Load the notes tree from each ref listed in 'refs'.  The output is
  * an array of notes_tree*, terminated by a NULL.
  */
-struct notes_tree **load_notes_trees(struct string_list *refs);
+struct notes_tree **load_notes_trees(struct string_list *refs, int flags);
 
 /*
  * Add all refs that match 'glob' to the 'list'.

t/t3301-notes.sh

@@ -83,6 +83,16 @@ test_expect_success 'edit existing notes' '
 	test_must_fail git notes show HEAD^
 '
 
+test_expect_success 'show notes from treeish' '
+	test "b3" = "$(git notes --ref commits^{tree} show)" &&
+	test "b4" = "$(git notes --ref commits@{1} show)"
+'
+
+test_expect_success 'cannot edit notes from non-ref' '
+	test_must_fail git notes --ref commits^{tree} edit &&
+	test_must_fail git notes --ref commits@{1} edit
+'
+
 test_expect_success 'cannot "git notes add -m" where notes already exists' '
 	test_must_fail git notes add -m "b2" &&
 	test_path_is_missing .git/NOTES_EDITMSG &&