Closes #2662

Only show recent push event if the branch still exists or a recent merge request has not been created

Closes #2277

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This method encapsulates all the logic for disabling 2FA on a specific
User model.

- Removes looking up authors/committers by name
- Renames `User.find_for_commit` to `User.find_by_any_email`

Now it executes a single query instead of a possible three at the cost
of some scary-looking ARel calls.

Closes https://github.com/gitlabhq/gitlabhq/issues/9328

To prevent loose of group data you need to transfer or remove group
first before you can remove user
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

**What does this do?**
It removes the very strict sanitation on the users bio field, so that people can
have a bio like "I <3 GitLab"

**Why is this needed?**
Currently when you enter a bio with "I <3 GitLab", we only store "I ". This is
unexpected behaviour, since we want users to have a normal profile, without
having to worry what characters are allowed and which are not.

**Related issues:**
Fixes https://github.com/gitlabhq/gitlabhq/issues/5625Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Now there is a single source of information for which attribute a model
uses to be referenced, and its special character.