Handling renames: svn vs. git vs. mercurial

Question

How do each of these VCS handle renames?

I have found a lot of contradicting information stating that git tracks LOC (lines of code) instead of files, renames would

Answer 1

In practice:

Git detects renames automatically. (Incidentally, I've heard claims that git can detect when you move a function from one file to another. My initial tests seem to indicate that this is not the case, however.)

With Mercurial, you have to explicitly tell it about renames, either by hg mv, or the --similarity option of hg addremove, or TortoiseHg's "guess renames" option, or certain tools e.g. VisualHg will flag the renames for you. If you want to use the Git approach with Mercurial, I've written an extension to detect renames at commit time, but it's at a very experimental stage at the moment.

Subversion doesn't handle renames at all. It records a rename as one file being removed and another file being added. This means, for instance, that if Alice changes a file and Bob renames it, you get a tree conflict. This happens whether you are doing full-blown branching and merging or simply svn update. Rename tracking is planned for Subversion 1.8, due out next year sometime.