CLIs are great when the space of actions you could perform is large (to nigh uncountable), but the range of subjects is small (the file paths, etc are known). Since you know the subjects, a programming language like `sh` is the most concise way to express a complex action.
GUIs are better in the exact opposite case: when you have a constrained set of actions to perform, but a large number of subjects they may be performed on. In that case, the problem isn't expressing the action, it's picking which subjects to act on (pick these lines to commit, oh except let me edit that one, put that one aside, ok back to the commit i'm staging...).
Many complex tools like VCSes contain both kinds of situations. I think sometimes a CLI is more appropriate, and sometimes a GUI is, depending on the context. IMO a fully mature VCS should make it as easy to invoke a gui for complex tasks as it is to do them from the command line.