Merge branch 'jt/repo-structure-extrema' into next

Merge branch 'jt/repo-structure-extrema' into next

"git repo structure" command learns to report maximum values on
various aspects of objects it inspects.

* jt/repo-structure-extrema:
  builtin/repo: find tree with most entries
  builtin/repo: find commit with most parents
  builtin/repo: add OID annotations to table output
  builtin/repo: collect largest inflated objects
  builtin/repo: add helper for printing keyvalue output
  builtin/repo: update stats for each object