This reverts commit 96bef54154e669f9a3e92c3a4bc76c0be3a52e48.

disable markdown in comments when referencing disabled features

fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/23548

This MR prevents the following references when tool is disabled:

- issues
- snippets
- commits - when repo is disabled
- commit range - when repo is disabled
- milestones

This MR does not prevent references to repository files, since they are just markdown links and don't leak
information.

See merge request !2011
Signed-off-by: NRémy Coutable <remy@rymai.me>

Commit 43d8bdb4 introduced additional
checks for permissions to read issue in references extractor.

According to endbosses' suggestions.

This reverts commit 5daf44b7, reversing
changes made to 2f706fbd.

This reverts commit 957e849f, reversing
changes made to 6b9dbe9f.
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

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

Remove emphasis from system notes to avoid Markdown conflicts in names.

Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Store both the project and identifier of extracted references.  This
prevents `ReferenceExtractor` from returning objects in the wrong
project for cross-project references.

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

Conflicts:
	CHANGELOG-EE

* project_with_code -> project
* project -> ermpty_project
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Any mention of Issues, MergeRequests, or Commits via GitLab-flavored markdown
references in descriptions, titles, or attached Notes creates a back-reference
Note that links to the original referencer. Furthermore, pushing commits with
commit messages that match a (configurable) regexp to a project's default
branch will close any issues mentioned by GFM in the matched closing phrase.
If accepting a merge request would close any Issues in this way, a banner is
appended to the merge request's main panel to indicate this.