Allow zeroPaddedFilemode git-fsck errors during git push

---

From: omnibus-gitlab#1602 (closed)

Git fsck is used for (too) many different repository integrity checks, including security problems. We've been using this when accepting git pushes into GitLab to detect malformed repositories.

The problem with this is that since we 'fsck' every push, GitLab has been rejecting repositories that get flagged by git fsck for non-security reasons such as zero-padded file modes. This prevents users from pushing certain legacy repositories to GitLab servers.

To let these users push their repositories to GitLab we should white-list the zeroPaddedFilemode fsck 'error'.

• add git config fsck.zeroPaddedFilemode ignore to the source installation guide
• check the value of fsck.zeroPaddedFilemode in https://gitlab.com/gitlab-org/gitlab-ce/blob/7bdcd6f3a1182e3b4354d6133fdc675c382aa94a/lib/system_check/app/git_config_check.rb
• update omnibus to set this git config value in its cookbook
• close omnibus-gitlab#1602 (closed)

---