[direnv] invalidate nix-direnv cache when flake inputs change (#10129)

Author: hawkw

.envrc

@@ -8,5 +8,12 @@ PATH_add out/mgd/root/opt/oxide/mgd/bin
 
 if [ "$OMICRON_USE_FLAKE" = 1 ] && nix flake show &> /dev/null
 then
+    # watch version files which should cause the nix-direnv cache to be
+    # invalidated, as they are inputs to the Nix flake.
+    watch_file tools/maghemite_mg_openapi_version
+    watch_file tools/dendrite_version
+    watch_file tools/clickhouse_version
+    watch_file tools/cocroachdb_version
+    watch_file rust-toolchain.toml
     use flake;
 fi