MergeBoard is a modern code review tool focused on helping developers understand code changes faster. The unique change visualization not only hides changes that do not affect the program flow, but also adds many useful annotations. You can directly see how code blocks were moved and which changes belong together.
MergeBoard offers its own UI for all code review related tasks, from opening a merge request till the final merge, and simply connects to your existing GitLab, GitHub or Bitbucket repositories. Integrations with external issue trackers and CI/CD pipelines make sure that you have all relevant information in one place.
Open source projects can use the SaaS version of MergeBoard for free.
Based on our record, Phabricator seems to be more popular. It has been mentiond 3 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
My company has used Phabricator, which is an alternative to Azure Devops, for about 5 years. A few days ago they announced that the project won't be maintained anymore, so we are looking into alternatives. We have around 50 devs+product folks that use Phabricator at the moment. Source: almost 3 years ago
You also mention Gitlab is close to what you would like - maybe Phabricator is even closer: https://phacility.com/phabricator/. Source: about 3 years ago
Https://phacility.com/phabricator/ I think checks most of those boxes, maybe all. Source: about 3 years ago
Atlassian Crucible - Collaborative peer code review tool.
GitLab - Create, review and deploy code together with GitLab open source git repo management software | GitLab
Gerrit Code Review - OpenSource Git Code Review Tool
GitHub - Originally founded as a project to simplify sharing code, GitHub has grown into an application used by over a million people to store over two million code repositories, making GitHub the largest code host in the world.
Upsource - Upsource provides unified access to all your projects stored in Git, Perforce, Mercurial or Subversion.
BitBucket - Bitbucket is a free code hosting site for Mercurial and Git. Manage your development with a hosted wiki, issue tracker and source code.