Fix huge line height for diff files list
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1826

Backport relevant changes from gitlab-org/gitlab-ee!51

To do:

- [x] Update gitlab-shell

See merge request !1822

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

Fix github importer to handle empty issues

Documentation for Git LFS

Doc explaining how to use Git LFS, how to use Git LFS with GitLab, known issues and troubleshooting tips.

See merge request !1813

More labels since we get more specializations.

/cc @creamzy @ernstvn @dzaporozhets 

See merge request !1821

Correctly set comparison first commit when range includes a merge commit

Fixes #3207.

See merge request !1814