It's been more than a decade so I almost certainly oversimplified the problem. But to give an approximate explanation: Subversion's model of how branches work

It's been more than a decade so I almost certainly oversimplified the problem. But to give an approximate explanation: Subversion's model of how branches work is fundamentally different to git's model. In fact in a sense subversion doesn't have a concept of branches at all in its core data model. Subversion just gives you a directory tree with a linear history, and then makes it cheap to copy directories around. The recommended layout for a subversion repository looks something like this: - /tags - /tags/release-v1 - /tags/release-v2 - /branches - /branches/my-feature-branch - /trunk/... If you want to create a branch you just copy your trunk directory to a new name under /branches. In order to reliably merge back & forth between branches or between a branch and trunk (which are just directories in the repository), you need more than just finding the diff between the latest state of each branch; you really need to know about the historical relationships between them: When the directory was created what was it copied from, what other merges have happened since then? But this information - at least "what merges have already been done" literally wasn't tracked until about subversion 1.5 (which was actually contemporaneous with a lot of the migrations of subversion to git, at least in my recollection). Some references for you: - The classic "svn book" about branching: https://svnbook.red-bean.com/en/1.7/svn.branchmerge.using.html https://svnbook.red-bean.com/en/1.7/svn.branchmerge.using.ht... - note the section at the bottom "The Key Concepts Behind Branching" which notes "First, Subversion has no internal concept of a branch—it knows only how to make copies. When you copy a directory, the resultant directory is only a “branch” because you attach that meaning to it." - The subversion 1.5 release notes explanation of merge tracking: https://subversion.apache.org/docs/release-notes/1.5.html#merge-tracking https://subversion.apache.org/docs/release-notes/1.5.html#me... To try to place this in time, I was using subversion (and was pretty happy with it!) in 2007. By 2009 I was using git wherever I could. Of course, the widespread migration toward git throughout the open source ecosystem was spread over a lot more years than this. But hopefully that gives some context.