Add option to update one dependency

[kfish]

When I work on a project which consists of both a library and a program in separate git repos, a common workflow is to:

1. add a feature to the library, commit and push it
2. run elm-install in the program dir, to update the dependency
3. use the new feature

However, step 2 takes a long time, because elm-install checks all the dependencies for updates. I specifically know that my own library has updated, and I am really only interested in updating that.

Would it be possible to add an option to check for updates for a specific dependency?

In the meantime, is there a quick way I can emulate this (eg. doing a 'git fetch' in ~/.elm-install/..., then a git checkout in elm-stuff/packages)?

[gdotdesign]

This a complex issue which I don't really know how to resolve.

Basically there is a cache of git repositories in ~/.elm-install/, we can use that cache to install the dependencies. The question is when to invalidate the cache, but there are several ways that the repository can be used:

• by version
• by referencing a tag / branch or specific commit (refs)

We could just compare the versions of the remote with our local ones using git ls-remote which is somewhat faster (not much) than git fetch (which happens now), this would work for the versions but not for refs. That's why every repository is updated every time.

So the ideal solution to speed it up would be a quick (even dirty) was of checking if a local repository is different from the remote, but I'm not aware of any that would do it.

---

The other way to go is to have some option / action:

1. --skip-updates - this would just use the cache or clone if not found
2. update-package user/package - this would fetch the given package directly
3. --update-only user/package - this would only update the given package

I'm in favor of 1. and 2. so it would go something like this:

elm-install update-package user/package && em-install --skip-updates

---

For your use case you could to use the directory option so you can use both locally when developing and only push versions when necessary.

[gdotdesign]

Also this issue might affect your install time: #42

[gdotdesign]

I've implemented 1. and 3. form above, so now you can use: elm-install --only-update elm-lang/core

Released as 1.6.0

[kfish]

Awesome, thanks!