Do not watch vendor/ for changes.

[rwjblue]

This fixes the polling regression that was added in #562 (broccoli-bower was doing this internally).

On my rMBP this change takes a super simple app (https://github.com/rjackson/_____ember-cli-test) from ~9% CPU usage down to ~2% (during ember server).

[rwjblue]

I believe that this resolves the performance issue that @krisselden mentioned recently.

[stefanpenner]

does this also then not watch files explicitly added from vendor? e.g. app.import('vendor/foo/bar.js')

if so, we must find a solution for this, or we will have many sad plugin authors.

[rwjblue]

app.import('vendor/foo/bar.js') will still work just fine, but if you change vendor/foo/bar.js you will need to restart your server.

Not sure why that would sadden folks, also this was the behavior prior to #562.

[rwjblue]

I view vendor/ essentially as an analogue to node_modules/: it is generally not OK to edit those files manually. In addition we are specifically ignoring all of vendor/ via our .gitignore, so any changes/modifications made to those files would be lost upon next cloning.

[stefanpenner]

@rjackson bower link/npm link are part of normal development workflows. When one makes such changes it is very important that we provide nice fast feedback.

It seems like files explicitly imported should be watched.

[rwjblue]

@stefanpenner - When you run npm link do you expect a long running task that had previously started to get the updated package? I would assume not (as I do not know how that would even be possible). How is this different?

[rwjblue]

I will think about how to get the explicitly added files watched.

[stefanpenner]

I think the only solution is to watch files that are explicitly imported. I believe the issue, is when we end up watching much much much larger tree's.

But I believe this is very important for our addon story, both for authors and consumers.

[rwjblue]

I have updated this PR to do as you have asked. It will now watch the directory containing the file being imported (there is no way currently to watch a specific file only). This still results in a much lower CPU consumption than master, and is definitely a win.

[stefanpenner]

@rjackson any ideas to watch specific files?

[rwjblue]

@stefanpenner - Yes, I am working on it, but it will have to be updated in Broccoli (working on refactoring the Broccoli::Watcher). This is still a pretty good quick win in the meantime.

[stefanpenner]

thanks @rjackson :)

[tonywok]

Nice! My poor little macbook air's fan thanks you. 👍