Verify version during build

[HelloGrayson]

Let's verify that the glide.Version matches the changelog - this will force us to update this value before releasing and prevent #629 from happening again.

To use this correctly, you must:

1. The latest version listen in the CHANGELOG must match glide.Version.
2. -dev can optionally be added to glide.Version.
3. The latest unreleased version must be listed in the CHANGELOG.

We've used this strategy successfully in:

• https://github.com/yarpc/yarpc-go
• https://github.com/thriftrw/thriftrw-go

cc @mattfarina

[HelloGrayson]

This first build should fail, verifying the feature. Once it does, I'll update the value of glide.Version to make it pass.

[prashantv]

can unexport this

[HelloGrayson]

Might be useful for exterior libs to be able to get at this, in the case that they use glide as a lib.

[prashantv]

I'd prefer to keep the visibility the same as it was previously as part of this change.

However since this is a main package, other's can't import it anyway.

[HelloGrayson]

Point taken - I updated to maintain the old api!

[sdboyer]

i haven't thought through all the implications of this, but in general it seems like a great idea

[HelloGrayson]

@sdboyer the implications is that the build will fail if go.version do not match the latest version in the changelog. In practice, this means catching issues like #629 from happening.

[sdboyer]

@breerly yes, that i understand - that's the intended effect. when i use "implication," i'm referring to potential second-order, unintended effects.

this isn't a knock against the PR; it's just a caveat about the depth of my review.

[mattfarina]

By changing from a var to const the ldflags for -X main.version=${VERSION} no longer works in the make build. This is why it was a var in the first place.

I think this needs to be switched back.

[HelloGrayson]

Sure

[mattfarina]

Once make build can pass the version into the code again this looks ready.

I like having this check.

[HelloGrayson]

Got it, I'll switch back to var

[mattfarina]

@breerly thanks for the contribution.