Mercurial SCM. Git. Git - How to use the subtree merge strategy. There are situations where you want to include contents in your project from an independently developed project.
You can just pull from the other project as long as there are no conflicting paths. The problematic case is when there are conflicting files. Potential candidates are Makefiles and other standard filenames. You could merge these files but probably you do not want to. Apache Subversion.