formatting: Update solc, param underscores

src/ERC20Helper.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0-only
-pragma solidity ^0.8.7;
+pragma solidity 0.8.7;
 
 import { IERC20Like } from "./interfaces/IERC20Like.sol";
 
@@ -22,15 +22,15 @@ library ERC20Helper {
         return _call(token_, abi.encodeWithSelector(IERC20Like.transferFrom.selector, from_, to_, amount_));
     }
 
-    function approve(address token, address spender, uint256 amount) internal returns (bool success_) {
+    function approve(address token_, address spender_, uint256 amount_) internal returns (bool success_) {
         // If setting approval to zero fails, return false.
-        if (!_call(token, abi.encodeWithSelector(IERC20Like.approve.selector, spender, uint256(0)))) return false;
+        if (!_call(token_, abi.encodeWithSelector(IERC20Like.approve.selector, spender_, uint256(0)))) return false;
 
-        // If `amount` is zero, return true as the previous step already did this.
-        if (amount == uint256(0)) return true;
+        // If `amount_` is zero, return true as the previous step already did this.
+        if (amount_ == uint256(0)) return true;
 
-        // Return the result of setting the approval to `amount`.
-        return _call(token, abi.encodeWithSelector(IERC20Like.approve.selector, spender, amount));
+        // Return the result of setting the approval to `amount_`.
+        return _call(token_, abi.encodeWithSelector(IERC20Like.approve.selector, spender_, amount_));
     }
 
     function _call(address token_, bytes memory data_) private returns (bool success_) {

src/interfaces/IERC20Like.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0-only
-pragma solidity ^0.8.7;
+pragma solidity 0.8.7;
 
 /// @title Interface of the ERC20 standard as needed by ERC20Helper.
 interface IERC20Like {

src/test/ERC20Helper.t.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0-only
-pragma solidity ^0.8.7;
+pragma solidity 0.8.7;
 
 import { DSTest } from "../../lib/ds-test/src/test.sol";
 

src/test/mocks/ERC20Mocks.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0-only
-pragma solidity ^0.8.7;
+pragma solidity 0.8.7;
 
 contract ERC20TrueReturner {
 

src/test/utils/InvariantTest.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: AGPL-3.0-only
-pragma solidity ^0.8.7;
+pragma solidity 0.8.7;
 
 contract InvariantTest {