refactor: re-introduce else clauses

I make the distinction between early returns and "either-or" cases when
it is about if-else clauses.

Here we have an "either-or" case. Either there is an exchange, then do
one thing, or if there is no exchange, do the other thing.

src/index.js

@@ -59,8 +59,9 @@ class BlockService {
   put (block) {
     if (this.hasExchange()) {
       return this._bitswap.put(block)
+    } else {
+      return this._repo.blocks.put(block)
     }
-    return this._repo.blocks.put(block)
   }
 
   /**
@@ -72,8 +73,9 @@ class BlockService {
   putMany (blocks) {
     if (this.hasExchange()) {
       return this._bitswap.putMany(blocks)
+    } else {
+      return this._repo.blocks.putMany(blocks)
     }
-    return this._repo.blocks.putMany(blocks)
   }
 
   /**
@@ -85,8 +87,9 @@ class BlockService {
   get (cid) {
     if (this.hasExchange()) {
       return this._bitswap.get(cid)
+    } else {
+      return this._repo.blocks.get(cid)
     }
-    return this._repo.blocks.get(cid)
   }
 
   /**
@@ -102,10 +105,10 @@ class BlockService {
 
     if (this.hasExchange()) {
       return this._bitswap.getMany(cids)
+    } else {
+      const getRepoBlocks = map((cid) => this._repo.blocks.get(cid))
+      return getRepoBlocks(cids)
     }
-
-    const getRepoBlocks = map((cid) => this._repo.blocks.get(cid))
-    return getRepoBlocks(cids)
   }
 
   /**