add documentation for startPrank and stopPrank (#606)

Author: anishnaik

Diff for: docs/src/SUMMARY.md

@@ -55,6 +55,8 @@
   - [setNonce](./cheatcodes/set_nonce.md)
   - [coinbase](./cheatcodes/coinbase.md)
   - [prank](./cheatcodes/prank.md)
+  - [startPrank](./cheatcodes/start_prank.md)
+  - [stopPrank](./cheatcodes/stop_prank.md)
   - [prankHere](./cheatcodes/prank_here.md)
   - [ffi](./cheatcodes/ffi.md)
   - [addr](./cheatcodes/addr.md)

Diff for: docs/src/cheatcodes/cheatcodes_overview.md

@@ -42,6 +42,12 @@ interface StdCheats {
     // Sets the *next* call's msg.sender to be the input address
     function prank(address) external;
 
+    // Sets all subsequent call's msg.sender (until stopPrank is called) to be the input address
+    function startPrank(address) external;
+
+    // Stops a previously called startPrank
+    function stopPrank() external;
+
     // Set msg.sender to the input address until the current call exits
     function prankHere(address) external;
 

Diff for: docs/src/cheatcodes/start_prank.md

@@ -0,0 +1,50 @@
+# `startPrank`
+
+## Description
+
+The `startPrank` cheatcode will set the `msg.sender` for all subsequent calls until `stopPrank` is called. This is in
+contrast to [`prank`](./prank.md) where `prank` only applies to the _next_ message call.
+
+## Example
+
+```solidity
+contract TestContract {
+    address owner = address(123);
+    ImportantContract ic;
+    AnotherImportantContract aic;
+
+    function deployImportantContract() public {
+        require(msg.sender == owner);
+
+        // Deploy important contract
+        ic = new ImportantContract(msg.sender);
+    }
+
+    function deployAnotherImportantContract() public {
+        require(msg.sender == owner);
+
+        // Deploy important contract
+        ic = new AnotherImportantContract(msg.sender);
+    }
+
+    function test() public {
+        // Obtain our cheat code contract reference.
+        IStdCheats cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);
+
+        // Prank and deploy important contracts
+        cheats.startPrank(owner);
+        deployImportantContract();
+        deployAnotherImportantContract();
+        cheats.stopPrank();
+
+        assert(ic.owner() == owner);
+        assert(aic.owner() == owner);
+    }
+    }
+```
+
+## Function Signature
+
+```solidity
+function startPrank(address) external;
+```

Diff for: docs/src/cheatcodes/stop_prank.md

@@ -0,0 +1,11 @@
+# `stopPrank`
+
+## Description
+
+Stops an active prank started by [`startPrank`](./start_prank.md), resetting `msg.sender`
+
+## Function Signature
+
+```solidity
+function stopPrank() external;
+```