feat(nix): nix and back again

I tried Nix, but it had too many downsides so I removed it.

1. Didn't like that all files are immutable and simple config changes
need a complete rebuild.
2. Setting up a new Mac didn't work as smoothly as promised. Not worth
the effort.
3. It sucked a lot to always have to type in the password twice on each
darwin-rebuild
4. It solves problems I never had.

.gitmux.conf

@@ -0,0 +1,28 @@
+tmux:
+    symbols:
+        branch: '  '
+        hashprefix: ': '
+        ahead: ' '
+        behind: ' '
+        staged: '󰉀 '
+        conflict: ' '
+        untracked: ' '
+        modified: ' '
+        stashed: ' '
+        clean: ' '
+    styles:
+        clear: '#[fg=default]'
+        state: '#[fg=red,bold]'
+        branch: '#[fg=white,bold]'
+        remote: '#[fg=cyan]'
+        staged: '#[fg=green,bold]'
+        conflict: '#[fg=red,bold]'
+        modified: '#[fg=red,bold]'
+        untracked: '#[fg=magenta,bold]'
+        stashed: '#[fg=cyan,bold]'
+        clean: '#[fg=green,bold]'
+        divergence: '#[fg=default]'
+    layout: [branch, divergence, ' ', flags]
+    options:
+        branch_max_len: 0
+        branch_trim: right