add halt height details

testnet/upgrades/v4.2.0/README.md

@@ -5,17 +5,36 @@ This upgrade follows the state export the network, so that we are using the same
 ### Release Details
 * Go version has been frozen at `1.21`. If you are going to build `terpd` binary from source, make sure you are using the right GO version!
 
-### Exported state 
+## Halt height 
+This upgrade requires `terpd` halting execution at a pre-selected halt-height. Failing to stop at halt-height may cause a consensus failure during chain execution at a later time.
 
-The snapshot of the state was taken at block height [], by the following command:
-```sh
-terpd export --height 3578710 --for-zero-height >> 90u-3-export.json
+There are two mutually exclusive options for this stage:
+
+### Option 1: Set the halt height by modifying app.toml
+- Stop the terpd process.
+- Edit the application configuration file at `~/.terp/config/app.toml` so that halt-height reflects the upgrade plan:
+```yaml
+# Note: Commitment of state will be attempted on the corresponding block.
+halt-height = 3686838
+```
+- restart terpd process
+- Wait for the upgrade height and confirm that the node has halted
+
+### Option 2: Restart the terpd binary with command line flags
+- Stop the terpd process.
+- Do not modify `app.toml`. Restart the terpd process with the flag `--halt-height`:
+```
+terpd start --halt-height 3686838
 ```
+- Wait for the upgrade height and confirm that the node has halted
 
-removing the logs from the result file, the snapshot's resulting checksum then becomes:
+Upon reaching the halt-height you need to replace the `v4.2.0`terpd binary with the new terpd `v4.2.0` binary and remove the halt-height constraint. Depending on your setup, you may need to set halt-height = 0 in your app.toml before resuming operations.
+
+### Exported state 
+
+The snapshot of the state was taken at block height [3686837](https://testnet.itrocket.net/terp/block/3686837), one block before the halt height, by the following command:
 ```sh
-sha256sum 90u-3-export.json
-#  8ef745fcbccbe4fe393a913fa71179e561cab82d45133003d0b454ce33f8d4c3  90u-3-export.json
+terpd export --height 3686837 --for-zero-height >> 90u-3-export.json
 ```
 
 # Performing the co-ordinated upgrade
@@ -33,12 +52,13 @@ sudo cp -r $HOME/.terp $HOME/.terp.backup
 
 reset local node directory
 ```sh 
-terpd tendermint unsafe-reset-all --home $HOME/.terp
+terpd tendermint unsafe-reset-all --home $HOME/.terp 
 ```
 download the new genesis file 
 ```sh
 wget -O $HOME/.terp/config/genesis.json https://raw.githubusercontent.com/hard-nett/networks/90u-3/testnet/90u-3/genesis.json
 ```
+
 configure new peers 
 ```sh
 SEEDS="e3f7a6a37f9b1bc7648603360b24312493c031f1@testnet-peer.terp.network:26656"
@@ -63,6 +83,6 @@ terpd start # starts the v4.2.0 node
 ```
 
 if all is well, remove the backup state 
-```
+```shell
 rm -rf $HOME/.terp.backup
 ```