Add reference to multichain deployment (#1414)

* Add reference to multichain deployment

* nits

---------

Co-authored-by: zerosnacks <[email protected]>

src/forge/deploying.md

@@ -4,7 +4,7 @@ Forge can deploy smart contracts to a given network with the [`forge create`](..
 
 Forge CLI can deploy only one contract at a time.
 
-For deploying and verifying multiple smart contracts in one go, Forge's [Solidity scripting](../tutorials/solidity-scripting.md#deploying-our-contract) would be the more efficient approach.
+For deploying and verifying multiple smart contracts on multiple chains in one go, Forge's [Solidity scripting](../tutorials/solidity-scripting.md#deploying-our-contract) would be the more efficient approach.
 
 To deploy a contract, you must provide a RPC URL (env: `ETH_RPC_URL`) and the private key of the account that will deploy the contract.
 
@@ -52,6 +52,50 @@ $ forge create --rpc-url <your_rpc_url> \
     src/MyToken.sol:MyToken
 ```
 
+## Multi-chain deployments
+
+Deploying and verifying multiple smart contracts on multiple chains in one go is possible by using forking cheatcodes.
+
+For example, if you want to deploy a `Counter` contract on Sepolia Mainnet and Base Sepolia using a single command, you can configure RPC endpoints and verifiers as:
+
+```toml
+[rpc_endpoints]
+sepolia = "${SEPOLIA_URL}"
+base-sepolia = "${BASE_SEPOLIA_URL}"
+
+[etherscan]
+sepolia = { key = "${SEPOLIA_KEY}" }
+base-sepolia = { key = "${BASE_SEPOLIA_KEY}" }
+```
+
+and create a `CounterScript` script as:
+
+```solidity
+contract CounterScript is Script {
+    function run() public {
+        vm.createSelectFork("sepolia");
+        vm.startBroadcast();
+        new Counter();
+        vm.stopBroadcast();
+
+        vm.createSelectFork("base-sepolia");
+        vm.startBroadcast();
+        new Counter();
+        vm.stopBroadcast();
+    }
+}
+```
+
+When running:
+
+```sh
+$ forge script script/CounterScript.s.sol --slow --multi --broadcast --private-key <your_private_key> --verify
+```
+
+The script will create the Sepolia Mainnet fork (`vm.createSelectFork("sepolia")`), deploy and verify the `Counter` contract, and then move to Base Sepolia chain deployment (`vm.createSelectFork("base-sepolia")`).
+
+For a list of all available forking cheatcodes see [`forking`](../cheatcodes/forking.md) docs.
+
 ## Verifying a pre-existing contract
 
 It is recommended to use the `--verify` flag with `forge create` to automatically verify the contract on explorer after a deployment.
@@ -62,18 +106,20 @@ If you are verifying an already deployed contract, read on.
 You can verify a contract on Etherscan, Sourcify, oklink or Blockscout with the [`forge verify-contract`](../reference/forge/forge-verify-contract.md) command.
 
 You must provide:
+
 - the contract address
 - the contract name or the path to the contract `<path>:<contractname>`
 - your Etherscan API key (env: `ETHERSCAN_API_KEY`) (if verifying on Etherscan).
 
 Moreover, you may need to provide:
+
 - the constructor arguments in the ABI-encoded format, if there are any
 - external linked libraries in `src_file_path:library_name:library_address` format, if there are any
 - [compiler version](https://etherscan.io/solcversions) used for build, with 8 hex digits from the commit version prefix (the commit will usually not be a nightly build). It is auto-detected if not specified.
-- the number of optimizations, if the Solidity optimizer was activated.  It is auto-detected if not specified.
+- the number of optimizations, if the Solidity optimizer was activated. It is auto-detected if not specified.
 - the [chain ID](https://evm-chainlist.netlify.app/), if the contract is not on Ethereum Mainnet
 
-Let's say you want to verify `MyToken` (see above). You set the [number of optimizations](../reference/config/solidity-compiler.md#optimizer_runs) to 1 million, compiled it with v0.8.10, and deployed it, as shown above, to the Sepolia testnet (chain ID: 11155111). Note that `--num-of-optimizations` will default to 0 if not set on verification, while it defaults to 200 if not set on deployment, so make sure you pass `--num-of-optimizations 200` if you left the default compilation settings. 
+Let's say you want to verify `MyToken` (see above). You set the [number of optimizations](../reference/config/solidity-compiler.md#optimizer_runs) to 1 million, compiled it with v0.8.10, and deployed it, as shown above, to the Sepolia testnet (chain ID: 11155111). Note that `--num-of-optimizations` will default to 0 if not set on verification, while it defaults to 200 if not set on deployment, so make sure you pass `--num-of-optimizations 200` if you left the default compilation settings.
 
 Here's how to verify it:
 
@@ -86,21 +132,23 @@ forge verify-contract \
     --etherscan-api-key <your_etherscan_api_key> \
     --compiler-version v0.8.10+commit.fc410830 \
     <the_contract_address> \
-    src/MyToken.sol:MyToken 
+    src/MyToken.sol:MyToken
 
 Submitted contract for verification:
                 Response: `OK`
                 GUID: `a6yrbjp5prvakia6bqp5qdacczyfhkyi5j1r6qbds1js41ak1a`
                 url: https://sepolia.etherscan.io//address/0x6a54…3a4c#code
 ```
 
-> ℹ️  **Note:**
-> 
-> External libraries can be specified with `--libraries` argument, one for each linked library. For example, to verify a contract with two linked libraries (`Maths` and `Utils`) the `forge verify-command` should be run with 
+> ℹ️ **Note:**
+>
+> External libraries can be specified with `--libraries` argument, one for each linked library. For example, to verify a contract with two linked libraries (`Maths` and `Utils`) the `forge verify-command` should be run with
+>
 > ```bash
 > --libraries src/lib/Maths.sol:Maths:<maths_lib_address> \
 > --libraries src/lib/Utils.sol:Utils:<utils_lib_address>
 > ```
+>
 > arguments.
 
 It is recommended to use the [`--watch`](../reference/forge/forge-verify-contract.md#verify-contract-options) flag along
@@ -117,7 +165,7 @@ Contract successfully verified.
 <br>
 
 > 💡 **Tip**
-> 
+>
 > Use Cast's [`abi-encode`](../reference/cast/cast-abi-encode.md) to ABI-encode arguments.
 >
 > In this example, we ran `cast abi-encode "constructor(string,string,uint8,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000` to ABI-encode the arguments.
@@ -131,37 +179,43 @@ Contract successfully verified.
 Make sure the private key string begins with `0x`.
 
 ##### `EIP-1559 not activated`
+
 EIP-1559 is not supported or not activated on the RPC server. Pass the `--legacy` flag to use legacy transactions instead of the EIP-1559 ones. If you do development in a local environment, you can use Hardhat instead of Ganache.
 
 ##### `Failed to parse tokens`
+
 Make sure the passed arguments are of correct type.
 
 ##### `Signature error`
+
 Make sure the private key is correct.
 
 ##### `Compiler version commit for verify`
+
 If you want to check the exact commit you are running locally, try: ` ~/.svm/0.x.y/solc-0.x.y --version` where `x` and
-`y` are major and minor version numbers respectively.  The output of this will be something like:
+`y` are major and minor version numbers respectively. The output of this will be something like:
 
 ```ignore
 solc, the solidity compiler commandline interface
 Version: 0.8.12+commit.f00d7308.Darwin.appleclang
 ```
 
-Note: You cannot just paste the entire string "0.8.12+commit.f00d7308.Darwin.appleclang" as the argument for the compiler-version.  But you can use the 8 hex digits of the commit to look up exactly what you should copy and paste from [compiler version](https://etherscan.io/solcversions).
+Note: You cannot just paste the entire string "0.8.12+commit.f00d7308.Darwin.appleclang" as the argument for the compiler-version. But you can use the 8 hex digits of the commit to look up exactly what you should copy and paste from [compiler version](https://etherscan.io/solcversions).
 
 ### Known Issues
 
 #### Verifying Contracts With Ambiguous Import Paths
 
 Forge passes source directories (`src`, `lib`, `test` etc) as `--include-path` arguments to the compiler.
 This means that given the following project tree
+
 ```text
 |- src
 |-- folder
 |--- Contract.sol
 |--- IContract.sol
 ```
+
 it is possible to import `IContract` inside the `Contract.sol` using `folder/IContract.sol` import path.
 
 Etherscan is not able to recompile such sources. Consider changing the imports to use relative import path.
@@ -171,4 +225,4 @@ Etherscan is not able to recompile such sources. Consider changing the imports t
 Currently, it's not possible to verify contracts on Etherscan with [`bytecode_hash`](../reference/config/solidity-compiler.md#bytecode_hash)
 set to `none`.
 Click [here](https://docs.soliditylang.org/en/v0.8.13/metadata.html#usage-for-source-code-verification) to learn more about
-how metadata hash is used for source code verification. 
+how metadata hash is used for source code verification.