Codegen in --watch mode doesn't handle deletions/renames fully

[brabeji]

Intended outcome:

--watch is able to track added, deleted and renamed files.

Actual outcome:

Currently only changes in preexisting files trigger watch.

How to reproduce the issue:
Try to create a query file matching includes pattern.

Further info:
There are two parts to this problem:

1. Watching logic is insufficient (no deletion and rename handling at least):
   

   apollo-tooling/packages/apollo/src/commands/client/codegen.ts

   Line 219 in a30f0e1

   watcher.on("all", (event, file) => {

2. Even after quick fix I made locally to handle specific cases:

...
            watcher.on("changed", (file) => {
                console.log('Watch event: changed', file);
                this.project.fileDidChange(vscode_uri_1.default.file(file).toString());
            });
            watcher.on("deleted", (file) => {
                console.log('Watch event: deleted', file);
                this.project.fileWasDeleted(vscode_uri_1.default.file(file).toString());
            });
            watcher.on("added", (file) => {
                console.log('Watch event: added', file);
                this.project.fileDidChange(vscode_uri_1.default.file(file).toString());
            });
            watcher.on("renamed", (file, newFile) => {
                console.log('Watch event: renamed', file);
                this.project.fileWasDeleted(vscode_uri_1.default.file(file).toString());
                this.project.fileDidChange(vscode_uri_1.default.file(newFile).toString());
            });
...

the result is not satisfactory. For example deletion of enclosing folder doesn't trigger file deletion. Gaze lib used for watching seems quite unreliable in edge-cases.
Also it doesn't handle globs with relative paths (--includes './src/**/*.gql').

[JakeDawkins]

We're working on trying out @atom/watcher watcher right now to support larger codebases. If we find it's performant enough, I'll take a look at adding in handlers for deletion and renames.

That may be tough though, since deleting/renaming files containing types could be an issue. I'll mention more later on if we move forward.

Also it doesn't handle globs with relative paths (--includes './src/**/*.gql').

this will be fixed with the release of #1007