notes: allow treeish expressions as notes ref

init_notes() is the main point of entry to the notes API. It ensures
that the input can be used as ref, because it needs a ref to update to
store notes tree after modifying it.

There however are many use cases where notes tree is only read, e.g.
"git log --notes=...".  Any notes-shaped treeish could be used for such
purpose, but it is not allowed due to existing restriction.

Allow treeish expressions to be used in the case the notes tree is going
to be used without write "permissions".  Add a flag to distinguish
whether the notes tree is intended to be used read-only, or will be
updated.

With this change, operations that use notes read-only can be fed any
notes-shaped tree-ish can be used, e.g. git log --notes=notes@{1}.

Signed-off-by: Mike Hommey <mh@glandium.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/notes.h b/notes.h
index 2a3f923380..e5d67fd375 100644
--- a/notes.h
+++ b/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;
@@ -72,6 +73,13 @@ 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
  * variable is used, and if that is missing, the default notes ref is used
@@ -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'.