…nged` while rollback at a special height (backport tendermint#2136) (tendermint#2457)

This is an automatic backport of pull request tendermint#2136 done by
[Mergify](https://mergify.com).


---


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Co-authored-by: Ethan <cosinlinker@gmail.com>

…ermint#2459) (tendermint#2464)

This is an automatic backport of pull request tendermint#2459 done by
[Mergify](https://mergify.com).


---


<details>
<summary>Mergify commands and options</summary>

<br />

More conditions and actions can be found in the
[documentation](https://docs.mergify.com/).

You can also trigger Mergify actions by commenting on this pull request:

- `@Mergifyio refresh` will re-evaluate the rules
- `@Mergifyio rebase` will rebase this PR on its base branch
- `@Mergifyio update` will merge the base branch into this PR
- `@Mergifyio backport <destination>` will backport this PR on
`<destination>` branch

Additionally, on Mergify [dashboard](https://dashboard.mergify.com) you
can:

- look at your merge queues
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Finally, you can contact us on https://mergify.com
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Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>

…nged` while rollback at a special height (backport tendermint#2136) (tendermint#2611)

closes: tendermint#2137 tendermint#1074

## Description
Rollback at a specific height causes the node to fail to start. This is
caused by the error code:

https://github.com/cometbft/cometbft/blob/635d0b596c7300c98caa57e7aab26a7a4579ab97/internal/state/rollback.go#L71

According to the definition of the `State` struct as below

https://github.com/cometbft/cometbft/blob/635d0b596c7300c98caa57e7aab26a7a4579ab97/internal/state/state.go#L63
`LastHeightValidatorsChanged` satisfy the following condition under any
circumstances
1 <= `state.LastHeightValidatorsChanged` <= `state.LastBlockHeight + 1 +
1`

this condition can also be confirmed by looking at the code in `func
(store dbStore) save(state State, key []byte) error`

https://github.com/cometbft/cometbft/blob/635d0b596c7300c98caa57e7aab26a7a4579ab97/internal/state/store.go#L229

`state.LastHeightValidatorsChanged` is with `nextHeight +
1`(`state.LastBlockHeight + 1 + 1`) corresponds.


When we rollback from block height `state.LastHeightValidatorsChanged -
1` to height `state.LastHeightValidatorsChanged - 2`,
`newState.LastHeightValidatorsChanged` would be wrong to modified into
the `state.LastHeightValidatorsChanged - 1`
 

## Issue
Let me give an example to describe the issue:

### example
> ... => [block 242 (5validators)] ==state1(5validators)==> [block 243
(5validators)] ==state2(4validators)==> [block 244 (4validators)] => ...
 
1. Assume that the current height of the block is 243, current state is
`state2` and `state2.LastHeightValidatorsChanged` == 244, validatorSet
changed to 4 validators in the block 244 and state2

2. Rollback to block 242 and state1, the target `rollbackHeight` == 242

3. Since the error code,
https://github.com/cometbft/cometbft/blob/635d0b596c7300c98caa57e7aab26a7a4579ab97/internal/state/rollback.go#L71
`state1.LastHeightValidatorsChanged` was changed to 243 incorrectly and
it should be 244

4. After rollbacked to block 242, node could not start properly

## Solution
See code for details.


#### PR checklist

- [x] Tests written/updated
- [ ] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [x] Updated relevant documentation (`docs/` or `spec/`) and code
comments
- [x] Title follows the [Conventional
Commits](https://www.conventionalcommits.org/en/v1.0.0/) spec
<hr>This is an automatic backport of pull request tendermint#2136 done by
[Mergify](https://mergify.com).

Co-authored-by: Ethan <cosinlinker@gmail.com>

…ermint#2459) (tendermint#2612)

<hr>This is an automatic backport of pull request tendermint#2459 done by
[Mergify](https://mergify.com).

---------

Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>