saving uncommitted changes in /etc prior to emerge run

profile.d/nix.sh

@@ -0,0 +1,31 @@
+if [ -n "$HOME" ]; then
+    NIX_LINK="$HOME/.nix-profile"
+
+    # Set the default profile.
+    if ! [ -L "$NIX_LINK" ]; then
+        echo "creating $NIX_LINK" >&2
+        _NIX_DEF_LINK=/var/lib/nix/profiles/default
+        /bin/ln -s "$_NIX_DEF_LINK" "$NIX_LINK"
+    fi
+
+    export PATH=$NIX_LINK/bin:$NIX_LINK/sbin:$PATH
+
+    # Subscribe the user to the Nixpkgs channel by default.
+    if [ ! -e $HOME/.nix-channels ]; then
+        echo "https://nixos.org/channels/nixpkgs-unstable nixpkgs" > $HOME/.nix-channels
+    fi
+
+    # Append ~/.nix-defexpr/channels/nixpkgs to $NIX_PATH so that
+    # <nixpkgs> paths work when the user has fetched the Nixpkgs
+    # channel.
+    export NIX_PATH=${NIX_PATH:+$NIX_PATH:}nixpkgs=$HOME/.nix-defexpr/channels/nixpkgs
+
+    # Set $SSL_CERT_FILE so that Nixpkgs applications like curl work.
+    if [ -e /etc/ssl/certs/ca-bundle.crt ]; then # Fedora, NixOS
+        export SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt
+    elif [ -e /etc/ssl/certs/ca-certificates.crt ]; then # Ubuntu, Debian
+        export SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
+    elif [ -e "$NIX_LINK/etc/ca-bundle.crt" ]; then # fall back to Nix profile
+        export SSL_CERT_FILE="$NIX_LINK/etc/ca-bundle.crt"
+    fi
+fi