Just finished first version of comment edit history plugin, source code is here: https://github.com/abitmore/steem/tree/dev-comment-history-plugin

### How to use

1- Compile

In local steemd directory,

```
git remote add abit https://github.com/abitmore/steem.git
git fetch abit
git checkout v0.14.2
git merge abit/dev-comment-history-plugin
git submodule update --init --recursive
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DENABLE_CONTENT_PATCHING=OFF -DLOW_MEMORY_NODE=ON ..
make steemd
```

2- Edit config.ini, enable the plugin and API:
```
# Set an API to be publicly available, may be specified multiple times
public-api = database_api login_api comment_history_api

# Plugin(s) to enable, may be specified multiple times
enable-plugin = witness comment_history
```

3- Start steemd with --rpc-endpoint and --replay
```
cd /parent/path/to/data
/path/to/steemd -s seed.steemed.net:2001 --rpc-endpoint --replay
```

4- Query

```
wscat -c ws://127.0.0.1:8090/ws/
> {"id": 1, "jsonrpc": "2.0", "method": "call", "params": [2, "get_comment_history", ["bluehorseshoe","a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak"]]}
< {"id":1,"result":[{"author":"bluehorseshoe","permlink":"a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak","block":5783105,"trx_in_block":2,"op_in_trx":0},{"author":"bluehorseshoe","permlink":"a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak","block":5783119,"trx_in_block":2,"op_in_trx":0},{"author":"bluehorseshoe","permlink":"a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak","block":5783196,"trx_in_block":3,"op_in_trx":0},{"author":"bluehorseshoe","permlink":"a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak","block":5783265,"trx_in_block":5,"op_in_trx":0},{"author":"bluehorseshoe","permlink":"a-simple-how-to-charcoal-grill-a-damn-good-t-bone-steak","block":5783468,"trx_in_block":5,"op_in_trx":0}]}
```
With this API we can get the block number and the transaction id in the block and operation id in the transaction, then we can use `get_block` API to get more detailed data.

### TODO
* return detailed data directly? If do, return patched content or the diff only? 

Please advice.

//Update 1:
Related feature request on github: https://github.com/steemit/steemit.com/issues/21