[feature request] Add dependency change only mode

[pzuraq]

Running into this with the ember-decorators library. Currently, the library is set up as a monorepo that consists of many addon packages, managed by lerna. This setup works well, but is very slow for testing. Even after consolidating all of the tests into the "main" ember-decorators package, it still takes twice as long as it would for a standard addon.

This is due to a double install occuring - first, lerna runs its install on every package via lerna bootstrap, and then links them up. Second, we run ember try:one in the main addon, which installs everything again.

I think ideally we would add a mode where you could only apply the diff to package.json in a given addon. Then, in our case, we would run the diff command first, then run lerna bootstrap, and have everything be installed and linked correctly in one go.

I'd be willing to open a PR for adding this if it seems like an acceptable feature.

[kategengler]

We discussed this in chat, but since it was in Discord 👏 I was able to find it in history to summarize here:

• There will still be a double install because ember-try needs to be installed to run
• Short term, could make a lerna dependency adapter
• Would also like to provide the ability to override install steps (cc @rwjblue)
• Long term, an ember-try standalone cli would allow it to be installed globally and avoid a double install

[pzuraq]

❤️ discord, thanks for getting this down @kategengler!