Update ExternalIssue regex for JIRA integration

The pattern in the `::reference_pattern` class method in the
ExternalIssue model does not match all valid forms of JIRA project
names. I have updated the regex to match JIRA project names with numbers
and underscores. More information on valid JIRA project names can be
found here:
https://confluence.atlassian.com/jira/changing-the-project-key-format-192534.html

* The first character must be a letter,
* All letters used in the project key must be from the Modern Roman Alphabet and upper case, and
* Only letters, numbers or the underscore character can be used.

1 files changed, 11 insertions, 0 deletions

diff --git a/spec/lib/gitlab/closing_issue_extractor_spec.rb b/spec/lib/gitlab/closing_issue_extractor_spec.rb
index 99288da1e43..04cf11fc6f1 100644
--- a/spec/lib/gitlab/closing_issue_extractor_spec.rb
+++ b/spec/lib/gitlab/closing_issue_extractor_spec.rb
@@ -135,6 +135,17 @@ describe Gitlab::ClosingIssueExtractor, lib: true do
         message = "resolve #{reference}"
         expect(subject.closed_by_message(message)).to eq([issue])
       end
+
+      context 'with an external issue tracker reference' do
+        it 'extracts the referenced issue' do
+          jira_project = create(:jira_project, name: 'JIRA_EXT1')
+          jira_issue = ExternalIssue.new("#{jira_project.name}-1", project: jira_project)
+          closing_issue_extractor = described_class.new jira_project
+          message = "Resolve #{jira_issue.to_reference}"
+
+          expect(closing_issue_extractor.closed_by_message(message)).to eq([jira_issue])
+        end
+      end
     end
 
     context "with a cross-project reference" do