Implement :wa[ll] command (write all)

[mleech]

Implements a basic :wa[ll] command (http://vimdoc.sourceforge.net/htmldoc/editing.html#:wall)
It currently just triggers vscode's workbench.action.files.saveAll command, so the bang version (wa!) doesn't overwrite readonly files.

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[johnfn]

Is this a WIP? I still see some TODO comments.

[mleech]

@johnfn I think it is useful in it's current form as partial implementation of :wa (at least it'd be useful for me 😃 :wa is ingrained in my muscle memory). The TODOs are more to call out what's missing re mimicking Vim fully. I'm a bit of a vscode noob so I'm not sure if they're possible with the current API.

[rebornix]

You can access textEditor.document.isUntitled to see if it's untitled.

[rebornix]

Two tiny comments and all others are good to me.

[johnfn]

LGTM; however ping @markrendle about @rebornix's comment about EOF. And can you bring this up to date with master?

[mleech]

Thanks @johnfn, it should be now up to date with master.
Also, I found the vscode.workspace.saveAll(includeUntitled: boolean) function in the vscode namespace, so I'm using that instead as it's cleaner and handles ignoring the untitled files.
Re @rebornix's EOF concern in the parsing code - that code is copied from the quit command and seems to be working. The call to scanner.next() doesn't get hit unless there are characters after the main command (:wa or :wall) so the call should always return something other than EOF.

[rebornix]

@mleech I see, thanks for helping understand the code better :) LGTM as well. Rebase the code and let's ship it!

[jpoon]

Thanks @mleech. I realized following the merge a better name for the class/filename may be writeall such that it follows suit with the others.

[mleech]

@jpoon yeah you're right, it would be a better name. I mistakenly thought all the other classes/files were named after the long version of the vim command - hence wall. I'll try and fix it up when I get some spare time.