refactor(library,hott): define 'congr' in the initialization files

hott/init/logic.hlean

@@ -61,6 +61,9 @@ namespace eq
   end ops
 end eq
 
+theorem congr {A B : Type} {f₁ f₂ : A → B} {a₁ a₂ : A} (H₁ : f₁ = f₂) (H₂ : a₁ = a₂) : f₁ a₁ = f₂ a₂ :=
+eq.subst H₁ (eq.subst H₂ rfl)
+
 section
   variables {A : Type} {a b c: A}
   open eq.ops

library/init/logic.lean

@@ -57,6 +57,9 @@ namespace eq
   end ops
 end eq
 
+theorem congr {A B : Type} {f₁ f₂ : A → B} {a₁ a₂ : A} (H₁ : f₁ = f₂) (H₂ : a₁ = a₂) : f₁ a₁ = f₂ a₂ :=
+eq.subst H₁ (eq.subst H₂ rfl)
+
 section
   variables {A : Type} {a b c: A}
   open eq.ops

library/logic/eq.lean

@@ -58,9 +58,6 @@ section
   theorem congr_arg (f : A → B) (H : a = a') : f a = f a' :=
   H ▸ rfl
 
-  theorem congr {f g : A → B} (H₁ : f = g) (H₂ : a = a') : f a = g a' :=
-  H₁ ▸ H₂ ▸ rfl
-
   theorem congr_arg2 (f : A → B → C) (Ha : a = a') (Hb : b = b') : f a b = f a' b' :=
   congr (congr_arg f Ha) Hb