SS5: move updateRelativeLink hook after concatination

[xini]

This is to make the relative actually updatable.

This picks up #2677 again for SS5.

[GuySartorelli]

There are CI failures to address.

[GuySartorelli]

What, ultimately, is the intention here?

[xini]

The intention is to be able to actually update the relative link. If the link is concatenated after the hook, you can't update the final link.

[GuySartorelli]

We'll need some words about this in the changelog but the PR that adds the 5.0.0 changelog file hasn't been merged yet. I won't let that hold up this change - instead I'll make a note for myself to add that to the changelog once it exists.

[GuySartorelli]

SiteTreeExtension includes a method signature for updateRelativeLink(&$base, &$action) - can you please update both the method signature and the PHPdoc in that extension?

Looks like in core there's no other instance of that method being defined - there might be in some of the supported modules but we haven't started looking at those yet for CMS 5

[xini]

Done. Sorry I missed that.

[GuySartorelli]

Changelog PR: silverstripe/developer-docs#75