Rename command

[martskins]

I was trying to implement the rename command, with a decent amount of success, until I found that you had a branch (rename) for it with some advancements on it.

Is that branch going somewhere or should I just submit a PR with my implementation?

[Ruin0x11]

I did have some progress going on the rename command, until I came across the issue of renaming classes. In IntelliJ the file containing the class is automatically renamed if you rename the class. However, from what I can remember the LSP client will not receive any information that the file was renamed and will continue to send updates about the previously renamed file, causing strange issues. I looked around for an LSP notification that would contain information about files that may have been renamed so the client can have knowledge of them, but currently there is no such notification. A proposal has been made at microsoft/vscode-languageserver-node#295 for adding such a notification to the spec, but it doesn't seem to be getting much attention. Apparently the rename operation wasn't even supported in VS Code for some time due to the same reason of lack of an API (microsoft/TypeScript#6487), but it did eventually get implemented through an unofficial extension. In the meantime before anything official is released, the rename command could just be implemented in the same way as VS Code/Che through an extension. In that case the changes in the existing branch could be used, just with another new command indicating renamed files. Of course, the client would have to be updated with this knowledge also.