Document how to upgrade a specific package

[carolynvs]

The README explains how to update everything but now how to update a single package. There is already explanation in the help text for this (see dep ensure -examples) but its a common enough case that we should highlight it. Let's add info on dep ensure -update foo and dep ensure -update [email protected] in the README as well, so that people are more likely to know that it exists.

[stephenafamo]

Can I work on this @carolynvs

[carolynvs]

@stephenafamo Yup! FYI, in the future no need to ask if no one else has "claimed" it yet. Just leave a comment that you are going to work on it. 😀

[stephenafamo]

How is dep ensure -update [email protected] supposed to work.
I keep getting
version constraint ^1.2.0 passed for github.com/some/package, but -update follows constraints declared in Gopkg.toml, not CLI arguments

[stephenafamo]

@carolynvs please take a look at the comment above

[darkowlzz]

@stephenafamo I don't think specifying a version constraint to -update is supported yet. The help says:

update the named dependencies (or all, if none are named) in Gopkg.lock to the latest allowed by Gopkg.toml (default: false)

"allowed by Gopkg.toml", so it refers to the constraint defined in Gopkg.toml. And that's the error you're get.

But I see it would be supported in a way in the future TODO.

[stephenafamo]

Okay. That's nice to know. It was confusing given the first post on this thread.

[carolynvs]

The issue was created before ensure was re-written. @stephenafamo Sorry I didn't catch that when you asked about this one a few days ago... 😞 I should have noticed and saved you some wasted time.

Closing as the README now does explain how to update a single package.