docs: clarify cosmovisor versions (cosmos#9989)

## Description

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This pull request adds clarification to the upgrade guide and cosmovisor documentation around cosmovisor versions.

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cosmovisor/README.md

@@ -1,21 +1,25 @@
 # Cosmosvisor Quick Start
 
-`cosmovisor` is a small process manager for Cosmos SDK application binaries that monitors the governance module via stdout for incoming chain upgrade proposals. If it sees a proposal that gets approved, `cosmovisor` can automatically download the new binary, stop the current binary, switch from the old binary to the new one, and finally restart the node with the new binary.
+`cosmovisor` is a small process manager for Cosmos SDK application binaries that monitors the governance module for incoming chain upgrade proposals. If it sees a proposal that gets approved, `cosmovisor` can automatically download the new binary, stop the current binary, switch from the old binary to the new one, and finally restart the node with the new binary.
 
 *Note: If new versions of the application are not set up to run in-place store migrations, migrations will need to be run manually before restarting `cosmovisor` with the new binary. For this reason, we recommend applications adopt in-place store migrations.*
 
+*Note: If validators would like to enable the auto-download option, and they are currently running an application using Cosmos SDK `v0.42`, they will need to use Cosmovisor [`v0.1`](https://github.com/cosmos/cosmos-sdk/releases/tag/cosmovisor%2Fv0.1.0). Later versions of Cosmovisor do not support Cosmos SDK `v0.42` or earlier if the auto-download option is enabled.*
+
 ## Contributing
 
-Release branches has the following format `release/cosmovisor/vA.B.x`, where A and B are a number (eg: `release/cosmovisor/v0.1.x`). Releases are tagged using the following format: `cosmovisor/vA.B.C`.
+Release branches have the following format `release/cosmovisor/vA.B.x`, where A and B are a number (e.g. `release/cosmovisor/v0.1.x`). Releases are tagged using the following format: `cosmovisor/vA.B.C`.
 
 ## Installation
 
-To install `cosmovisor`, run the following command:
+To install the latest version of `cosmovisor`, run the following command:
 
 ```
-go get github.com/cosmos/cosmos-sdk/cosmovisor/cmd/cosmovisor
+go install github.com/cosmos/cosmos-sdk/cosmovisor/cmd/cosmovisor@latest
 ```
 
+*Note: If you are using go `v1.15` or earlier, you will need to use `go get`, and you may want to run the command outside a project directory.*
+
 ## Command Line Arguments And Environment Variables
 
 All arguments passed to `cosmovisor` will be passed to the application binary (as a subprocess). `cosmovisor` will return `/dev/stdout` and `/dev/stderr` of the subprocess as its own. For this reason, `cosmovisor` cannot accept any command-line arguments other than those available to the application binary, nor will it print anything to output other than what is printed by the application binary.

docs/migrations/chain-upgrade-guide-043.md

@@ -24,15 +24,19 @@ Instead of starting a new chain, the upgrade binary will read the existing datab
 
 We recommend using [In-Place Store Migrations](../core/upgrade.html) to upgrade your chain from v0.42 to v0.43. The first step is to make sure all your modules follow the [Module Upgrade Guide](../building-modules/upgrade.html). The second step is to add an [upgrade handler](../core/upgrade.html#running-migrations) to `app.go`.
 
-In this document, we'll provide an example of what the upgrade handler looks like for a chain upgrading module versions for the first time. It's critical to note that the initial version of each module must be set to `1` rather than `0` or else the upgrade handler will re-initialize each module.
+In this document, we'll provide an example of what the upgrade handler looks like for a chain upgrading module versions for the first time. It's critical to note that the initial consensus version of each module must be set to `1` rather than `0` or else the upgrade handler will re-initialize each module.
 
 In addition to migrating existing modules, the upgrade handler also performs store upgrades for new modules. In the example below, we'll be adding store migrations for two new modules made available in v0.43: `x/authz` and `x/feegrant`.
 
 ## Using Cosmovisor
 
 We recommend validators use [Cosmovisor](../run-node/cosmovisor.html), which is a process manager for running application binaries. For security reasons, we recommend validators build their own upgrade binaries rather than enabling the auto-download option. Validators may still choose to use the auto-download option if the necessary security guarantees are in place (i.e. the URL provided in the upgrade proposal for the downloadable upgrade binary includes a proper checksum).
 
-Validators can use the auto-restart option to prevent unecessary downtime during the upgrade process. The auto-restart option will automatically restart the chain with the upgrade binary once the chain has halted at the proposed upgrade height. With the auto-restart option, validators can prepare the upgrade binary in advance and then relax at the time of the upgrade.
+::: tip
+If validators would like to enable the auto-download option, and they are currently running an application using Cosmos SDK `v0.42`, they will need to use Cosmovisor [`v0.1`](https://github.com/cosmos/cosmos-sdk/releases/tag/cosmovisor%2Fv0.1.0). Later versions of Cosmovisor do not support Cosmos SDK `v0.42` or earlier if the auto-download option is enabled.
+:::
+
+Validators can use the auto-restart option to prevent unnecessary downtime during the upgrade process. The auto-restart option will automatically restart the chain with the upgrade binary once the chain has halted at the proposed upgrade height. With the auto-restart option, validators can prepare the upgrade binary in advance and then relax at the time of the upgrade.
 
 ## Migrating app.toml
 
@@ -42,7 +46,9 @@ With the update to `v0.43`, new server configuration options have been added to
 
 The following example will walk through the upgrade process using `simapp` as our blockchain application. We will be upgrading `simapp` from v0.42 to v0.43. We will be building the upgrade binary ourselves and enabling the auto-restart option.
 
-*Note: In this example, we will be starting a new chain from `v0.42`. The binary for this version will be the genesis binary. For validators using Cosmovisor for the first time, the binary for the current version of the chain should be used as the genesis binary (i.e. the starting binary). For more information, see [Cosmovisor](../run-node/cosmovisor.html).*
+::: tip
+In the following example, we start a new chain from `v0.42`. The binary for this version will be the genesis binary. For validators using Cosmovisor for the first time on an existing chain, either the binary for the current version of the chain should be used as the genesis binary (i.e. the starting binary) or validators should update the `current` symbolic link to point to the upgrade directory. For more information, see [Cosmovisor](../run-node/cosmovisor.html).
+:::
 
 ### Initial Setup
 
@@ -108,12 +114,16 @@ Now that our node is initialized and we are ready to start a new `simapp` chain,
 
 ### Cosmovisor Setup
 
-First, install or update `cosmovisor`:
+Install the `cosmovisor` binary:
 
 ```
-go get github.com/cosmos/cosmos-sdk/cosmovisor/cmd/cosmovisor
+go install github.com/cosmos/cosmos-sdk/cosmovisor/cmd/cosmovisor@v0.1.0
 ```
 
+::: tip
+If you are using go `v1.15` or earlier, you will need to change out of the `cosmos-sdk` directory, run `go get` instead of `go install`, and then change back into the `cosmos-sdk` repository.
+:::
+
 Set the required environment variables:
 
 ```