When the call to the agent fails, we must retrieve the error message
just after the function call, as other calls may overwrite it.

As the agent authentication is the only one which has a teardown and
there does not seem to be a way to get the error message from a stored
error number, this tries to introduce some small changes to store the
error from the agent.

Clearing the error at the beginning of the loop lets us know whether the
agent has already set the libgit2 error message and we should skip it,
or if we should set it.

The callers of git_packfile_unpack() expect the obj_offset argument to
be set to the beginning of the next object. We were mistakenly returning
the the offset of the object's data, which causes the CRC function to
try to use the wrong offset.

Set obj_offset to curpos instead of elem->offset to point to the next
element and bring back expected behaviour.

The recv buffer (parse_buffer) and the buffer have independent sizes and
offsets. We try to fill in parse_buffer as much as possible before
passing it to the http parser. This is fine most of the time, but fails
us when the buffer is almost full.

In those situations, parse_buffer can have more data than we would be
able to put into the buffer (which may be getting full if we're towards
the end of a data sideband packet).

To work around this, we check if the space we have left on our buffer is
smaller than what could come from the network. If this happens, we make
parse_buffer think that it has as much space left as our buffer, so it
won't try to retrieve more data than we can deal with.

As the start of the data may no longer be at the start of the buffer, we
need to keep track of where it really starts (data_offset) and use that
in our calculations for the real size of the data we received from the
network.

This fixes #2518.

In the check for multiline, we traverse the backslashes from the end
backwards and int the end assert that we haven't gone past the beginning
of the line. We make sure of this in the loop condition, but we also
check in the return value.

However, for certain configurations, a line in a multiline variable
might be empty to aid formatting. In that case, 'end' == 'start', since
we ended up looking at the first char which made it a multiline.

There is no need for the (end > start) check in the return, since the
loop guarantees we won't go further back than the first char in the
line, and we do accept the first char to be the final backslash.

This fixes #2483.

This works around strict aliasing rules letting some versions of
GCC (particularly on RHEL 6) thinking that they can skip updating the
size of the array when calculating the next element's offset.

Preallocating two commits doesn't make much sense as leaving allocation
to the first array usage will allocate a sensible size with room for
growth.

This preallocation has also been hiding issues with strict aliasing in
the tests, as we have fairly simple histories and never trigger the
growth.

We used to assume a refspec would only have an asterisk in the middle of
their respective pattern. This has not been a valid assumption for some
time now with git.

Instead of assuming where the asterisk is going to be, change the logic
to treat each pattern as having two halves with a replacement bit in the
middle, where the asterisk is.

When transforming a non-pattern refspec, we simply need to copy over the
opposite string. Move that logic up to the wrapper so we can assume a
pattern refspec in the transformation function.

In order to connect to a remote server, we need to provide a path to the
repository we're interested in. Consider the lack of path in the url an
error.

When the stream writing function was written, it assume that
libssh2_channel_write() would always write all of the data to the
wire. This is only true for the first 32k of data, which it tries to
fit into one ssh packet.

Since it can perform short writes, call it in a loop like we do for
send(), advancing the buffer offset.

To make sure that items returned from pool allocations are aligned
on nice boundaries, this rounds up all pool allocation sizes to a
multiple of 8.  This adds a small amount of overhead to each item.

The rounding up could be made optional with an extra parameter to
the pool initialization that turned on rounding only for pools
where item alignment actually matters, but I think for the extra
code and complexity that would be involved, that it makes sense
just to burn a little bit of extra memory and enable this all the
time.

This lets a user decide they do want to use keyboard-interactive after
they've compiled.

When linking against libssh2, create the transport.h such that it
contains its definition for custom crypto and keyboard-interactive
callbacks.

If we don't link against libssh2, create an equivalent signature which
has void pointers instead of pointers to libssh2 structures.

This would be one way to fix #2438.

The OpenSSL library-loading functions do not expect to be called
multiple times. Add a flag in the non-threaded libgit2 init so we only
call once.

This fixes #2446.

treebuilder: set the attributes before sorting and inserting

We need to set the attributes before we try to insert it into the
vector, as the comparison function needs to know whether the entry is a
tree or not.

Don't use read-write accounts for the tests

netops: init OpenSSL once under lock

The assembla failure we were seeing referred to a private repository,
which is not what is there at the moment.

This reverts 1fd21b03

Don't write in plaintext the password of an account which has full
control over the repository. Instead use an account with read-only
access.

We want to check whether the credentials callback is NULL, not whether
the payload is.

Bring together all of the OpenSSL initialization to
git_threads_init() so it's together and doesn't need locks.

Moving it here also gives us libssh2 thread safety (when built against
openssl).

OpenSSL's tests init everything in the main thread, so let's do that.

When using in a multithreaded context, OpenSSL needs to lock, and leaves
it up to application to provide said locks.

We were not doing this, and it's just luck that's kept us from crashing
up to now.

Add docs for git_clone_local_t and move the docs for the
git_clone_options to each field.

The OpenSSL init functions are not reentrant, which means that running
multiple fetches in parallel can cause us to crash.

Use a mutex to init OpenSSL, and since we're adding this extra checks,
init it only once.

revwalk: more sensible array handling

Instead of using a sentinel empty value to detect the last commit, let's
check for when we get a NULL from popping the stack, which lets us know
when we're done.

The current code causes us to read uninitialized data, although only on
RHEL/CentOS 6 in release mode. This is a readability win overall.

treebuilder: insert sorted

By inserting in the right position, we can keep the vector sorted,
making entry insertion almost twice as fast.