bind git_reference_dwim
reference-branch? & reference-remote? predicates
branch-is-head? -> branch-head?
basic clone.h bindings & tests
more complete file-status tests
rest of refspec bindings
finish refspec bindings
basic remote & refspec tests
export commit-parent-id
revspec parsing
docs for revision parsing
simplify branch-name binding
fix branch-head? function name in tests
commit-ancestor
add commit-parents convenience function
clean up imports & move exports to dedicated file

This slightly reorganizes the import forms for git & git-lolevel, moves
git's export list into its own file, and adds an explicit export list
for git-lolevel (rather than just exporting everything), also in its own
file.
check pkg-config for libgit2 version information

This checks pkg-config for libgit2's version information before
installation (and exits early on a version mismatch), if it's available.
produce object files and an archive for static linking
fall back to repo-discover when initial repo-open fails
set finalizer on oids produced by oid-cpy