mathlib

e8ad2e38 - feat(category_theory/limits): the pullback of a monomorphism is a monomorphism (#2113)

feat(category_theory/limits): the pullback of a monomorphism is a monomorphism (#2113) * The pullback of a monomorphism is a monomorphism * The pushout of an epimorphism is an epimorphism * Fix a proof * renaming Co-authored-by: Scott Morrison <scott@tqft.net> Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>