Some tools create multiple author fields. git is rather lax when parsing
them, although fsck does complain about them. This means that they exist
in the wild.

As it's not too taxing to check for them, and there shouldn't be a
noticeable slowdown when dealing with correct commits, add logic to skip
over these extra fields when parsing the commit.

Introduce `git_filter_list_contains`

Correct line endings on winhttp.def

indexer: use lseek to extend the packfile

Fixed handling of GIT_DELTA_CONFLICTED  in git_diff_find_similar()

`git_filter_list_contains` can be used to query a filter list to
determine if a given filter will be run.

gitattributes: let clients use native line endings

git_diff_find_similar() now ignores git_diff_delta records with a status
of GIT_DELTA_CONFLICTED, which fixes a crash due to assert() being hit.

Use "text=auto" to ensure that we get LFs in the repository, but
let clients have their native line endings in their worktree.

A few more fixes from coverity

When we hit an error writing to the next stream from a file, we jump to
'done' which currently skips over closing the file descriptor.

Make sure to close the descriptor if it has been set to a valid value.

We take in a possibly partial ID by taking a length and working off of
that to figure out whether to just look up the object or ask the
backends for a prefix lookup.

Unfortunately we've been checking the size against `GIT_OID_HEXSZ` which
is the size of a *string* containing a full ID, whereas we need to check
against the size we can have when it's a 20-byte array.

Change the checks and comment to use `GIT_OID_RAWSZ` which is the
correct size of a git_oid to have when full.

The way we currently do it depends on the subtlety of strlen vs sizeof
and the fact that .pack is one longer than .idx. Let's use a git_buf so
we can express the manipulation we want much more clearly.

`merge_diff_list_count_candidates()` takes pointers to the source and
target counts, but when it comes time to increase them, we're increasing
the pointer, rather than the value it's pointing to.

Dereference the value to increase.

Rather minimal change, but it's the kind of thing we should do.

A few fixes from Coverity

Coverity complains about the git_rawobj ones because we use a loop in
which we keep remembering the old version, and we end up copying our
object as the base, so we want to have the data pointer be NULL.

Let `ssh_stream_free()` take a NULL stream, as free functions should,
and remove the check from the connection setup.

The connection setup would not need the check anyhow, as we always have
a stream by the time we reach this code.

Downcase

global: Ensure we free our SSL context.

path: error out if the callback returns an error

Fixed build warnings on Xcode 6.1

print_usage functions is defined but not used

When the callback returns an error, we should stop immediately. This
broke when trying to make sure we pass specific errors up the chain.

This broke cancelling out of the loose backend's foreach.

Change error when running out of ssh agent keys

Use the previously created function to display a message when the arguments are not valid.

ticket 3095

We've been using `p_ftruncate()` to extend the packfile in order to mmap
it and write the new data into it. This works well in the general case,
but as truncation does not allocate space in the filesystem, it must do
so when we write data to it.

The only way the OS has to indicate a failure to allocate space is via
SIGBUS which means we tried to write outside the file. This will cause
everyone to crash as they don't expect to handle this signal.

Switch to using `p_lseek()` and `p_write()` to extend the file in a way
which tells the filesystem to allocate the space for the missing
data. We can then be sure that we have space to write into.

This was forgotten when the feature was implemented.

build maint branches on appveyor

Implementation of url.*.insteadOf

A remote's URLs are now modified according to the url.*.insteadOf
and url.*.pushInsteadOf configurations. This allows a user to
replace URL prefixes by setting the corresponding keys. E.g.
"url.foo.insteadOf = bar" would replace the prefix "bar" with the
new prefix "foo".

Some brain damaged tolower() implementations appear to want to
take the locale into account, and this may require taking some
insanely aggressive lock on the locale and slowing down what should
be the most trivial of trivial calls for people who just want to
downcase ASCII.