notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond

The combine_notes_fn functions uses a non-zero return value to indicate
failure. However, this return value was converted to a call to die()
in note_tree_insert().

Instead, propagate this return value out to add_note(), and return it
from there to enable the caller to handle errors appropriately.

Existing add_note() callers are updated to die() upon failure, thus
preserving the current behaviour. The only exceptions are copy_note()
and notes_cache_put() where we are able to propagate the add_note()
return value instead.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Jonathan Nieder: Improve clarity of final if-condition in note_tree_insert()

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/notes-cache.c b/notes-cache.c
index dee6d62e72..4c8984ede1 100644
--- a/notes-cache.c
+++ b/notes-cache.c
@@ -89,6 +89,5 @@ int notes_cache_put(struct notes_cache *c, unsigned char key_sha1[20],
 
 	if (write_sha1_file(data, size, "blob", value_sha1) < 0)
 		return -1;
-	add_note(&c->tree, key_sha1, value_sha1, NULL);
-	return 0;
+	return add_note(&c->tree, key_sha1, value_sha1, NULL);
 }