This survived the last round of culling, as the signature is only in the
comments.

Fix wrong assertion

Fixes issue #2196

revwalk: don't try to find merge bases when there can be none

As a way to speed up the cases where we need to hide some commits, we
find out what the merge bases are so we know to stop marking commits as
uninteresting and avoid walking down a potentially very large amount of
commits which we will never see. There are however two oversights in
current code.

The merge-base finding algorithm fails to recognize that if it is only
given one commit, there can be no merge base. It instead walks down the
whole ancestor chain needlessly. Make it return an empty list
immediately in this situation.

The revwalk does not know whether the user has asked to hide any commits
at all. In situation where the user pushes multiple commits but doesn't
hide any, the above fix wouldn't do the trick. Keep track of whether the
user wants to hide any commits and only run the merge-base finding
algorithm when it's needed.

reflog: follow core.logallrefupdates

On bare by default, or when core.logallrefupdates is false, we must not
write the reflog.

Reflog all the way

Given HEAD -> master -> foo, when updating foo's reflog we should also
update HEAD's, as it's considered the current branch.

The reflog append function was overzealous in its checking. When passed
an old and new ids, it should not do any checking, but just serialize
the data to a reflog entry.

Remove some duplicated logic.

If the caller wants to update a ref to point to the same target as it
currently has, we should return early and avoid writing to the reflog.

The existing ones lack checking zeroed ids when switching back from an
unborn branch as well as what happens when detaching.

The reflog appending function mistakenly wrote zeros when dealing with a
detached HEAD. This explicitly checks for those situations and fixes
them.

Implement git_merge_base_octopus

Seamless support for NTLM/Kerberos auth on Windows

refs: append to the HEAD reflog when updating the current branch

Add a few projects to the list

When we update the current branch, we must also append to HEAD's reflog
to keep them in sync.

This is a bit of a hack, but as git.git says, it covers 100% of
default cases.

This is not something anybody would ever do; removing HEAD makes the
.git/ directory no longer be a repository, so we wouldn't be expected to
handle such a situation.

Fix pqueue sort boundary condition bug

If the pqueue comparison fn returned just 0 or 1 (think "a<b")
then the sort order of returned items could be wrong because there
was a "< 0" that really needed to be "<= 0".  Yikes!!!

Add git_submodule_resolve_url()

corrected typo in error message

Update clar to e1990d6

Rename options structures

Add a tag example

Fun with memory access

Plug leaks

We look up a reference in order to figure out if it's the current
branch, which we need to free once we're done with the check.

As a bonus, only perform the check when we're passed the force flag, as
it's a useless check otherwise.