I readily admit I am not familiar enough with fossil to know about the impedance mismatch, but I'll point out that https://github.com/JetBrains/intellij-plugins

I readily admit I am not familiar enough with fossil to know about the impedance mismatch, but I'll point out that https://github.com/JetBrains/intellij-plugins/tree/idea/241.13688.18/PerforceIntegration https://github.com/JetBrains/intellij-plugins/tree/idea/241.... https://github.com/JetBrains/intellij-community/tree/idea/241.13688.18/plugins/git4idea https://github.com/JetBrains/intellij-community/tree/idea/24... https://github.com/JetBrains/intellij-community/tree/idea/241.13688.18/plugins/hg4idea https://github.com/JetBrains/intellij-community/tree/idea/24... https://github.com/JetBrains/intellij-community/tree/idea/241.13688.18/plugins/svn4idea https://github.com/JetBrains/intellij-community/tree/idea/24... may a long way toward finding how they think about those operations and you may already know about it but https://github.com/irengrig/fossil4idea https://github.com/irengrig/fossil4idea (Apache 2) is the one listed in https://plugins.jetbrains.com/plugin/7479-fossil-integration https://plugins.jetbrains.com/plugin/7479-fossil-integration although as you pointed out, it's very stale