[jhvkjhk]

Compatible with old projects is the main reason why modern software suck, look at zsh, c++. Some times we need to shift to a brand new paradigm.

[HelloNurse]

Git (and less popular competitors that are close in age and design principles, like Mercurial, Darcs and Fossil) is what everyone is using and therefore what needs compatibility, not an "old project" holding back progress.

That role is filled by Subversion, CVS, VSS etc. with their tragic anti-features.