Require Git v2.18.0 across the board

In different MRs, we have the need to use flags and features (like --filter and --in-commit-order), only available for newer versions of git. In most of them, what we want to achieve is reducing heavy blob processing.

We currently support git versions >= 2.9.5. Should we consider bumping the supported git versions? We can benefit from the new features if we do it. Also, the majority of the supported version has many security vulnerabilities.