2.2.0-rc behavior changes (1/2)

I've been running a test suite we use to verify Git behaviors across versions, and the 2.2.0 RCs (0 and 1 both) have a couple of small behavioral differences. I'm sending them in separate e-mails just to make the contents easier to grok.

Important: It's entirely possible neither of these is a _bug_; they
may both be intentional changes in behavior.

First change: git update-ref -d /refs/heads/nonexistent <some-valid-sha1> now produces an error about ref locking that it didn't produce before

Git 2.1.x and prior produced this output: error: unable to resolve reference refs/heads/nonexistent: No such file or directory

Now, in the 2.2.0 RCs, it says: error: unable to resolve reference refs/heads/nonexistent: No such file or directory error: Cannot lock the ref 'refs/heads/nonexistent'.

This one feels more like a bug, but again may not be. I say it feels like a bug because of the order of the messages: If git has decided the ref doesn't exist, why is it still trying to lock it?

This change bisects to:

bturner@felurian:~/Development/git/git$ git bisect bad
7521cc4611a783f4a8174bd0fcec5f4a47357ac1 is the first bad commit
commit 7521cc4611a783f4a8174bd0fcec5f4a47357ac1
Author: Ronnie Sahlberg <sahlberg@google.com>
Date:   Wed Apr 30 09:22:45 2014 -0700

    refs.c: make delete_ref use a transaction

Best regards, Bryan Turner