Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

added better error handling. Also refactored some of the code and fixed a few issues in project_tree_saver

Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

# Conflicts:
#	app/models/project.rb

Remove `wall_enabled` field from Project



See merge request !4089

Improve multiple branch push performance by memoizing permission checking

See merge request !4091

Pass trusted_proxies to action_dispatch as IPAddrs instead of strings

Without this setting your own trusted_proxies does not work.

Fixes an issue introduce in: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3524

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/17004

See merge request !3970

If you attempt to push thousands of branches at once, the 60-second timeout
will occur because GitAccess checking does a lot of work to check if the
user has permission to push to a branch. This changes does two things:

1. Instead of making 1 DB query per branch push, use a memoized list of protected branches to check
2. Memoize what permissions the user has to perform on this project

On a test of 10,000 branch pushes, this prevents gitlab-shell from hitting the 60-second
timeout.

Closes #17225

Escape HTML in commit titles in system note messages

Closes #17348

See merge request !4084

Fix build notification on merge request page change even if the build status didn't change

## What does this MR do?
This MR contains a bugfix for #17357 which was introduced by !3998. The notification are now only shown on status changes, and not when switching between different merge requests.

## Are there points in the code the reviewer needs to double check?
Check implementation

## Why was this MR needed?
Because auf a bug introduced in !3998.

## What are the relevant issue numbers?
#17357

Closes #17357

See merge request !4086