Merge branch 'jc/unresolve' into next

* jc/unresolve:
Add git-unresolve <paths>...
get_tree_entry(): make it available from tree-walk
sha1_name.c: no need to include diff.h; tree-walk.h will do.
sha1_name.c: prepare to make get_tree_entry() reusable from others.
pre-commit hook: complain about conflict markers.
git-merge: a bit more readable user guidance.
diff: move diff.c to diff-lib.c to make room.
git log: don't do merge diffs by default
Allow "git repack" users to specify repacking window/depth

diff --cc .gitignore
Simple merge

diff --cc Makefile
Simple merge

diff --cc git.c
Simple merge