Cleaning various codepaths up.
* ds/more-index-cleanups:
t1092: test interesting sparse-checkout scenarios
test-lib: test_region looks for trace2 regions
sparse-checkout: load sparse-checkout patterns
name-hash: use trace2 regions for init
repository: add repo reference to index_state
fsmonitor: de-duplicate BUG()s around dirty bits
cache-tree: extract subtree_pos()
cache-tree: simplify verify_cache() prototype
cache-tree: clean up cache_tree_update()