Redmine

Description:
RedmineTextFormatting explains how to link to a specific revision number such as r123

But lets say you have a complex setup with a top level project containing several subprojects, and you want to link to a specific revision in a repository that is not attached to the same project as the wiki text you are editing (or rather a issue text)

Resolution:
If this feature exist, it should be documented in RedmineTextFormatting. If it does not exist, this is a feature request.

For example by using the project identifier (Project Settings->Information->Identifier) in combination with the revision, such as identifier:r123