fix: fail back to previous flake if upgrade fails

Signed-off-by: matttrach <matt.trachier@suse.com>

Author: matttrach

.envrc

@@ -36,8 +36,13 @@ if ! which "$0" | grep -q nix; then
     git checkout flake.lock
   fi
 
-  print 'Installing Nix Profile...'
-  nf profile install . --profile "$profile"
+  echo 'Installing Nix Profile...'
+  if ! nf profile install . --profile "$profile"; then
+    echo 'Failed to install new Nix profile! Reverting to previous profile...'
+    git checkout flake.lock
+    nf profile install . --profile "$profile"
+  fi
+
   nf profile list --profile "$profile"
 
   print 'Starting...'