Move file-moving logic from tree-view's MoveDialog to fsPlus.moveSync

[oclbdk]

As far as I can tell, the tree-view's MoveDialog is the only client of fsPlus.moveSync -- https://github.com/atom/tree-view/blob/48fd001687f14bb8538fe6c92f59d9774fa87c4f/lib/move-dialog.coffee#L31. It adds a lot of custom logic (e.g. checking when a move is valid, creating the target's parent directory if it doesn't exist, etc) that could be useful for other callers.

I'm specifically making this move so we can reuse the function for remote file support.

[oclbdk]

Regarding the possibility of breaking existing packages that rely on fs.moveSync throwing an error if the target's parent directory doesn't exist (or the other side effects from fs.renameSync)... it's trivial to change their calls from fs.moveSync to fs.renameSync.

I see fs.moveSync as a smarter helper method that's more useful than fs.renameSync in the same way that fs.remove supersedes fs.unlink and fs.rmdir.

[oclbdk]

I accidentally closed this pull request by hitting a keyboard shortcut, would still very much appreciate comments or a merge. :)

[kevinsawicki]

For things like this that might be built-in depending on the context, we try to use the global when available and fall back to the require when it isn't there.

So something like:

Promise = global.Promise ? require('es6-promise').Promise

[kevinsawicki]

This line and the line below it should use statSyncNoException for speed 🐎

Basically it removes the need for a try/catch and instead you can just return true if either oldStat or newStat is false.

[kevinsawicki]

Thanks for this! 🚢