Reduce logging
Update to upstream objective-git
Clean up build number handling
Update build scripts for Python 3
Ignore .xccheckout files
Disable zombie detection in the shared scheme
Unify build scripts
Ignore some python intermediates
Must use `--abbrev-ref` if we expect to get a branch name from `git rev-parse`
Fix new build script
Remove unnecessary working directory argument
Always use Scripting Bridge to invoke GUI from CLI

When the CLI command is invoked without any arguments or with some refs,
the CLI command was using a low-level NSAppleEventDescriptor to
communicate with the main GUI process. That behavior was inconsistent
with the behavior for other command-line options, where communication is
done with high-level Scripting Bridge. Moreover, the GUI side was
failing to handle the NSAppleEventDescriptor and thus ignoring command
line arguments passed from CLI (cf. https://github.com/rowanj/gitx/issues/196).

This commit modifies the code so that CLI and GUI always use Scripting
Bridge to send and receive command-line arguments correctly.
Don't recreate graphQueue

Recreating the graph queue means that the new queue may start a
background operation before the old queue is still running another
operation. Multiple operations being executed at the same time seem to
be causing an occasional crash because they are not synchronized.

Note that calling cancelAllOperations for the old queue does not abort
an operation that has already started.
Rev-parse refspecs when loading commits

The rev specifier strings may not always simple symbolic refs. They may
be SHA values or refs with some modifiers like HEAD~3^2. They needs to
be rev-parsed to load commits as expected.
Special refs should be added to others

Refs that are not branches, tags, nor remotes should be added to the
"others" list rather than the "branches" list.
PBGitRepository: use rev-parse in shaForRef

If the ref is a SHA string rather than an ordinary named ref, the
"referenceByLookingUpReferencedNamed:..." method doesn't find the
expected GTReference. The "lookupObjectByRevParse:..." method can be
used to parse SHA strings as well as named refs.