Local clone

Assert the exact amount of links we expect. While there, check that a
plain git_clone() automatically chooses to link.

[Blob] Update documentation for is_binary.

filter.h tells me that we check the first 8000 bytes.

If requested, git_clone_local_into() will try to link the object files
instead of copying them.

This only works on non-Windows (since it doesn't have this) when both
are on the same filesystem (which are unix semantics).

When passed the LINK_FILES flag, the recursive copy will hardlink files
instead of copying them.

A call like git_clone("./foo", "./foo1") writes origin's url as './foo',
which makes it unusable, as they're relative to different things.

Go with git's behaviour and store the realpath as the url.

When git is given such a path, it will perform a "local clone",
bypassing the git-aware protocol and simply copying over all objects
that exist in the source.

Copy this behaviour when given a local path.

index: check for valid filemodes on add

travis: build on osx too

Fixed permissions on template directories.

Fix compile error on Visual Studio

Introduce GIT_MERGE_CONFIG_* for merge.ff settings

git_merge_analysis will now return GIT_MERGE_CONFIG_NO_FASTFORWARD
when merge.ff=false and GIT_MERGE_CONFIG_FASTFORWARD_ONLY when
merge.ff=true

Fixed miscellaneous documentation errors.

We go through the different backends in order, so it's not an error if
at least one of the backends has the data we want.

We have too many places where we repeat free code, so when adding the
new free to the generic code, it didn't take for the local transport.

While there, fix a C99-ism that sneaked through.

Add support for the symref extension

Make core.safecrlf not generate an error on LF-ending platforms

Include windows.h on win32 for Sleep

smart: send a flush when we disconnect

Since we no longer need to push data to callbacks, there's no need for
this truct.

Let's use the remote's default branch guessing instead of reinventing
one ourselves with callbacks.

If the remote supports the symref protocol extension, then we return
that, otherwise we guess with git's rules.

When using the local transport, we always have the symbolic information
available, so fill it.

Add a symref_target field to git_remote_head to expose the symref
mappings to the user.

The protocol has a capability which allows the server to tell us which
refs are symrefs, so we can e.g. know which is the default branch.

This capability is different from the ones we already support, as it's
not setting a flag to true, but requires us to store a list of
refspec-formatted mappings.

This commit does not yet expose the information in the reference
listing.