GLM: support a shorthand reference project#123 instead of group/project#123 for projects in the same group

[http://docs.gitlab.com/ce/user/markdown.html#special-gitlab-references](GLM reference) reads:

That is, to reference an issue inside gitlab-org/omnibus-gitlab, we need to type gitlab-org/omnibus-gitlab#1. Result: omnibus-gitlab#1 (closed). Perfect!

I propose adding a shorthard syntax for referencing a different project inside the same group omnibus-gitlab#1. Result: omnibus-gitlab#1 (closed). Doesn't work now.

The rationale is pretty clear, when we mean omnibus-gitlab#1 (closed), everyone knows it's gitlab-org's ombibus-gitlab. It saves a lot of typing both in issues and commit messages. It also makes commit messages cleaner and more concise.

Added markdown label

How would you deal with forks of the same project where omnibus-gitlab#1 could be ambiguous?

@stanhu So the question is whether omnibus-gitlab#1 (closed) refers to stanhu/omnibus-gitlab#1 or omnibus-gitlab#1 (closed), right? If so, my answer is it refers to the upstream as long as there's a fork link. When it's deleted, it longer points there. Please note using a shorthand syntax with project name has less problems than using the shortest syntax - #1 (closed). In this case if repo is forked, it no longer points where it pointed to (or, let's say, it points to an issue that doesn't exist since issues aren't cloned, but in the future it'll point to issues created in that project, which will be totally random). Yet everyone's comfortable with #1 (closed) syntax although it may be ambiguous in forks. It's damn convenient to use #1 (closed), so would be omnibus-gitlab#1 (closed).

Worth noting ambiguity problem doesn't exist in non-open source work environments. Git "native" workflow isn't frequent, almost everyone does it the old SVN way - pushing directly to the upstream repo branches, or to master. Those infrequent forks always relate to the main repo anyways. Open source world is different and projects that are intended to be like hard-forked and reused should use the long form syntax and avoid both #1 (closed) and omnibus-gitlab#1 (closed) syntaxes.

Added ~874211 label

Added ~164274 label

Reassigned to @smcgivern

Mentioned in merge request !7255 (merged)

@smcgivern @Nowaker @DouweM Do you guys have any thoughts about converting omnibus-gitlab#1to a gitlab-org/omnibus-gitlab#1 link? It seems a straightforward presentation IMO.

@oswluizf to my mind, the collapsing presentation is the biggest benefit of this change! I'm very unlikely to type these links by hand, but having them be in a shorter format would be super-slick. And, in general, we should always show the shortest reference format that matches the reference.

What do you mean by converting? Do you mean even if a#1 is typed in, show it as b/a#1? I don't have a reasonable opinion about it yet but my gut feeling is #1 (closed) isn't displayed as a#1 so maybe it's best to leave a#1 as a#1 too.

Yes, the idea was that. But I agree with you on leaving the link text the same way it's initially typed (shorthand format).

EDIT: s/you/yet/. Sorry about that @oswluizf.

closed via commit e27fa5bc

mentioned in merge request !7110 (merged)

mentioned in merge request !8857