Streamline url-parsing logic.

update example to new packfile creation signature

Allow callers to set mode on packfile creation

Add git_packbuilder_hash to query pack filename

don't double free pkt

Change the git_branch_iterator_new definition to use git_branch_t

Plug configuration file search paths tests leaks

Plug git_merge() related leaks

merge!

Fix leaks

branch: move from foreach to an iterator

Preserve error messages during file system iterator cleanup

Create a git_branch_iterator type which is equivalent to the foreach but
lets us write loops instead of callbacks.

Since the introduction of git_reference_shorthand(), the added value of
passing the name is reduced.

Propagate ELOCKED error when updating the config

Take umask into account in filebuf_commit

When the filesystem iterator encounters an error with a file, it
returns the error but because of the cleanup code, it was in some
cases erasing the error message.  This uses the giterr_detach API
to make sure that the actual error message is restored after the
cleanup code has been run.

There are a number of cases where it is convenient to be able to
fetch and "claim" the current error string, clearing the error.
This is helpful when you need to call some code that may alter
the error and you want to restore it later on and/or report it via
some other mechanism.