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>
Notes provide a fast lookup mechanism for data keyed by
sha1. This is ideal for caching certain operations, like
textconv filters.
This patch builds some infrastructure to make it simpler to
use notes trees as caches. In particular, caches:
1. don't have arbitrary commit messages. They store a
cache validity string in the commit, and clear the tree
when the cache validity string changes.
2. don't keep any commit history. The accumulated history
of a a cache is just useless cruft.
3. use a looser form of locking for ref updates. If two
processes try to write to the cache simultaneously, it
is OK if one overwrites the other, losing some changes.
It's just a cache, so we will just end up with an extra
miss.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
