First version of the modifications guide

docs/src/content/ignition/docs/guides/modifications.md

@@ -1 +1,99 @@
 # Modifying an existing module
+
+If you have defined your modules and deployed them, you can still modify them.
+
+If we wanted to add a new `Rocket` to the module we deployed in the [Quick Start guide](../getting-started/index.md#quick-start), all we need to do is modifying the module definition like this
+
+::::tabsgroup{options="TypeScript,JavaScript"}
+
+:::tab{value="TypeScript"}
+
+**ignition/modules/Apollo.ts**
+
+```typescript{8,10,12}
+import { buildModule } from "@nomicfoundation/hardhat-ignition/modules";
+
+export default buildModule("Apollo", (m) => {
+  const apollo = m.contract("Rocket", ["Apollo"]);
+
+  m.call(apollo, "launch", []);
+
+  const starship = m.contract("Rocket", ["Starship"], { id: "starship" });
+
+  m.call(starship, "launch", []);
+
+  return { apollo, starship };
+});
+```
+
+:::
+
+:::tab{value="JavaScript"}
+
+**ignition/modules/Apollo.js**
+
+```javascript{8,10,12}
+const { buildModule } = require("@nomicfoundation/hardhat-ignition/modules");
+
+module.exports = buildModule("Apollo", (m) => {
+  const apollo = m.contract("Rocket", ["Apollo"]);
+
+  m.call(apollo, "launch", []);
+
+  const starship = m.contract("Rocket", ["Starship"], { id: "starship" });
+
+  m.call(starship, "launch", []);
+
+  return { apollo, starship };
+});
+```
+
+:::
+
+::::
+
+Then, we can run it just like the first time, and Hardhat Ignition will continue from where it left
+
+::::tabsgroup{options="TypeScript,JavaScript"}
+
+:::tab{value="TypeScript"}
+
+```sh
+npx hardhat ignition deploy ignition/modules/Apollo.ts --network localhost
+```
+
+:::
+
+:::tab{value="JavaScript"}
+
+```sh
+npx hardhat ignition deploy ignition/modules/Apollo.js --network localhost
+```
+
+:::
+
+::::
+
+and we'll get a result like this
+
+```
+Batch #1
+  Executed Apollo#starship
+
+Batch #2
+  Executed Apollo#Apollo.starship.launch
+
+
+[ Apollo ] successfully deployed 🚀
+
+Deployed Addresses
+
+Apollo#Rocket - 0x5fbdb2315678afecb367f032d93f642f64180aa3
+Apollo#starship - 0x9fe46736679d2d9a65f0992f2272de9f3c7fa6e0
+```
+
+with two new batches, that execute the new parts of the module, while keeping the previous results.
+
+## Incompatible modifications
+
+If you try to modify the definition of a `Future` that has already been partially or completely executed in an incompatible way, it may not be possible to resume your existing deployment. To learn more about this, please read the [Reconciliation](../advanced/reconciliation.md) guide.