Add option to turn off OpenSSL

git_merge_tree_flag_t cannot contain any GIT_DIFF_FIND_xxx flags so there's not point in checking for them

The implementation of the hashsig API disallows computing a signature on
small files containing only a few lines. This new flag disables this
behavior.

git_diff_find_similar() sets this flag by default which means that rename
/ copy detection of small files will now work. This in turn affects the
behavior of the git_status and git_blame APIs which will now detect rename
of small files assuming the right options are passed.

Use svg instead of png to get better image quality

clone example: don't divide by zero

Local transports don't have data about the size, avoid dividing by
zero in the callback.

This should provide a easier way to see what kinds of changes we have,
and a single place to look at the breaking changes.

  Fix crash in free() when git_buf_grow() fails.

Remove symlinks from the repository

remote: plug leak

Remove the hook symlink from the test resources, so that we can
have a source tree that is easy to zip up and copy around on systems
that don't support symlinks.  Create it dynamically at test execution
instead.

Load prune configuration when a remote is created.

CHANGELOG: we've added git_describe

submodule: declare vars at top of func block

Add appveyor yaml

CHANGELOG: add missing 0.22 changes

Better document `git_merge_commits`

The release after 0.21 is 0.22. Add a new heading for the changes since
0.22.

Bump the version number to 0.22.0 and the SOVERSION to 22.

`git_merge_commits` (and thus `git_merge`) do not use the same
strategy as `git-merge-recursive` wherein they can produce an
artificial common ancestor that is the merge of all common
ancestors.  Document this accordingly.

Fixed internal push state not being cleared when calling git_remote_download()