Add aliass for home-manager commands

I'm not entirely sure this whole rigamaroll was worth it, but basically
I noticed that for some reason Ansible was skipping doing the
home-manager derivation when running playbooks back-to-back. So I fixed
that, or so I think. To make sure the derivation only happens when the
repo is updated, I added an activation script to the home-manager
config. Yes, technically the Nix part of the repo could be untouched and
yet still trigger a rebuild, but that's fine. I hope this convoluted
logic tree doesn't break down.

homes/common.nix

@@ -65,10 +65,10 @@ in {
     };
     sessionPath = [ "$HOME/.local/bin" ];
     activation = {
-      recordHmGitHash = lib.hm.dag.entryAfter [ "writeBoundary" ] ''
+      rec-hm-git-hash = lib.hm.dag.entryAfter [ "writeBoundary" ] ''
         cd "$HOME/.config/home-manager" || exit 1
-        if [ -z "$(${pkgs.git}/bin/git status --porcelain --untracked-files=no)" ]; then
-          run echo "$(${pkgs.git}/bin/git rev-parse HEAD)" | tee $HOME/.cache/hm-git-hash
+        if [ -z "$(git status --porcelain --untracked-files=no)" ]; then
+          run echo "$(git rev-parse HEAD)" | tee $HOME/.cache/hm-git-hash
         else
           run echo '*' | tee $HOME/.cache/hm-git-hash
         fi