This reverts commit 5d65b4ebeb6b2294654b3562fb15d7fa94751522, because it broke git-add. See https://github.com/NixOS/nixpkgs/pull/38636#issuecomment-380182555 for details.
Git's Makefile has a NO_INSTALL_HARDLINKS flag to produce symlinks instead of hard links. However, it still produces hard links between $out/bin and $out/libexec, hence the patch. Also, update Git to 1.8.2.1.