git_tree_walk
export tag-peel
low-level branch bindings
high-level branch bindings
branch tests
branch docs
tree-walk docs
merge-base docs
tag-peel docs
Merge branch 'diff-api' into libgit2-0.17.0

Conflicts:
	git.scm
Merge branch 'libgit2-0.17.0'
release 0.17.0 updates & diff api changes
fix argument type in diff-file-mode docs
update history
ensure callback procedures aren't moved by the gc while in use
move trees to static memory before git_tree_walks
remove unnecessary call/cc
git_reference_foreach
reference-for-each docs
merge diff, branch & callback changes from libgit2-0.17.0