Allura supports merge requests for its Git and Hg functionality, but it could be made better. This would involve python, git, and hg. Also HTML/CSS/JS.
Here are some ideas for improvement, of varying difficulty:
- automatically update when new commits are pushed https://forge-allura.apache.org/p/allura/tickets/5993/
- preview commits https://forge-allura.apache.org/p/allura/tickets/6581/
- better display after merging https://forge-allura.apache.org/p/allura/tickets/7879/
- branch comparison https://forge-allura.apache.org/p/allura/tickets/5840/ and/or https://forge-allura.apache.org/p/allura/tickets/7241/
- commenting on individual lines/chunks of diffs https://forge-allura.apache.org/p/allura/tickets/7241/
- and more ... https://forge-allura.apache.org/p/allura/tickets/search/?q=labels%3Amerge-reguests+AND+status%3Aopen