SAST MR Widget displays wrong results

Summary

Originally reported via this ticket (internal only)

If a scan is running for the main branch and a newly created MR triggers a new scan; The MR widget will display "Security report is out of date." and also incorrectly report previously reported vulnerabilities

Steps to reproduce

In a sast enabled project:

• Trigger a pipeline in main
• While the previous one is running, create an MR

Example Project

This project can be used as an example

What is the current bug behavior?

Old vulnerabilities are displayed

What is the expected correct behavior?

Old vulnerabilities shouldn't be displayed

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Implementation Plan

• backend modify the base_pipeline (and merge_base_pipeline if necessary) method(s) called by comparison_base_pipeline to select the latest complete pipeline for use in the comparison of reports.