Fix 2FA authentication spoofing

This is security fix for vulnerability described at
https://gitlab.com/gitlab-org/gitlab-ce/issues/14900.

Attacker was able to bypass password authentication of users that have 2FA enabled, and consequently sign is as a different user, without knowing his password, if he managed to guess 2FA One Time Password for that user.

It was also possible to enumerate users and check if they have 2FA enabled, because GitLab responded with different error for each case.

This MR attempts to change default user search scope if `otp_user_id` session variable has been set. If it is present, it means that user has 2FA enabled, and has already been verified with login and password. In this case we should look for user with `otp_user_id` first, before picking it up by `login`.

Both, 2FA authentication spoofing and 2FA discovery have been covered by specs.

Current 2FA code is a bit tricky, so it probably needs some refactoring.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Don't fetch any tags from a forked repo

Closes #13957

See merge request !3504
Signed-off-by: Rémy Coutable <remy@rymai.me>

Bump Git version requirement to 2.7.4 (for 8.5)

[ci skip]

See merge request !3286

Install Git 2.7.3, not 2.4.3



See merge request !3248

Bump Git version requirement to 2.7.3

[ci skip]

See merge request !3240

[ci skip]

Use leases for LDAP checks in 8.5

Back-port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3143

See merge request !3181

Allow filtered explore results to be paged. Fixes #14104

See merge request !3149

Fix "Show all" link behavior

The "Show all" link was broken by recent refactors from @joshfng. I have fixed it very simply (I believe).

**Please note that this fix will be in 8.5.x only** (since the whole "Show all" stuff was moved to pagination recently (8.6).

Fixes #14168 

/cc @joshfng @dzaporozhets @razer6 

See merge request !3159

Fixes #14168

Fix error 500 in Todos

Closes #14095

Closes #14075

Closes #14109

Closes #14151

See merge request !3141

Only show group member roles if explicitly requested

This very simply fixes an EE problem, but I made the change here so it's less prone to errors from merges.

In EE, prior to this change, group member roles were shown in project member list when a project is shared with a group. This is bad because the project explicitly shares with the group and sets a 'max access' level. If the max access level is 'developer' the project owner doesn't want to see 'Owner' in the group roles because it will confuse them. I verified that permissions are really being honored here, it was just an error in the view. You can see in https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/views/projects/project_members/_shared_group_members.html.haml#L18 where this was how it was intended to be. Likely a CE-EE merge introduced this bug. That's why I made the boolean required in CE even though this is for EE.

![Screen_Shot_2016-03-01_at_8.59.02_AM](/uploads/704ab3149f60c363dd8374bd0c06a46a/Screen_Shot_2016-03-01_at_8.59.02_AM.png)

![Screen_Shot_2016-03-01_at_9.17.54_AM](/uploads/5fcabef352cbc41dade037767f90ace3/Screen_Shot_2016-03-01_at_9.17.54_AM.png)

See merge request !3044

[ci skip]

Invalidate cache for builds badge

This fixes cache issue with badges (we should not cache badge images).

Closes #13982

See merge request !3086

Flush repository caches before renaming projects

This should hopefully solve gitlab-org/gitlab-ce#13790. Once I know the exact steps to reproduce the problem I should be able to confirm this.

cc @dblessing @inem

See merge request !2974

Add Todos documentation

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/13884

See merge request !3064

Don't show "Welcome to GitLab" when the search didn't return any projects

Fixes #13785. /cc @pixdrift

### Before

![Screen_Shot_2016-03-02_at_10.55.02](/uploads/b6b6ead2143d01e374ad296e72182d79/Screen_Shot_2016-03-02_at_10.55.02.png)

### After

![Screen_Shot_2016-03-02_at_12.12.33](/uploads/6e16c44e69039c534ea0fc3373c6060b/Screen_Shot_2016-03-02_at_12.12.33.png)

See merge request !3059

Tag deletion doesn't use AJAX anymore

See merge request !2986

Fix permissions for deprecated CI build status badge

This fixes permissions for deprecated status badge, being unavailable even if project is public.

Closes #13324

See merge request !3030

Show days remaining instead of elapsed time for Milestone.

Closes #13623

See merge request !2978

Fix import from gitlab.com fails

_Originally opened at !2896 by @kazsw._

- - -

Fixes #12652

CGI.escape encodes '/' by default.
Second argument can be removed.

See merge request !2988

Fix help keyboard shortcut for relative URL setups

Fixes gitlab-org/gitlab-ce#12751

See merge request !3016

Fix relative URL

See https://github.com/gitlabhq/gitlabhq/issues/10053

 1. Same configuration way for relative URL like with Omnibus
 2. Loading the relative configuration from Rakefile as Rails do not load initializers for `asset:precompile`

First point has another positive side effect: no collisions (due to git controlled `application.rb`) any more during the upgrades of source based installations and relative url configuration

 - [x] tests on the source based installation
 - [x] tests on the centos&ubuntu omnibus packages

Fixes: gitlab-org/gitlab-ce#13730, gitlab-org/gitlab-ce#13727, gitlab-org/omnibus-gitlab#1143 and https://github.com/gitlabhq/gitlabhq/issues/10053

See merge request !2979

Fix issue with overlap of sidebar links.

Thanks @iamphill for the help with this one. 

![Screen_Shot_2016-03-01_at_10.19.52_AM](/uploads/f203fde79ae397ad18f23c4108f1c306/Screen_Shot_2016-03-01_at_10.19.52_AM.png)

cc @iamphill @alfredo1 @dzaporozhets @rymai 

See merge request !3043

Don't show any "2FA required" message if it's not actually required

Prior, if the user had enabled and then disabled 2FA, they would be
shown a "You must enable Two-factor Authentication for your account."
message when going back to re-activate it, even if 2FA enforcement was
disabled.

See merge request !3014

Improve implementation to check read access to forks and add pagination.

Fixes #13648

The following optimizations where made:

- Pagination was added.
- Code to check for read permissions to forks was optimized, in the past we were doing too many queries for each project.

See merge request !2991

Don't repeat labels listed on Labels tab.

Fixes #13622

See merge request !2924

Brings back missing "Gitlab" text on the logo

Closes #13851 

See merge request !2989