Clean up documentation for tracked files

README.md

@@ -278,15 +278,45 @@ will be interpeted or passed along.
 All single word arguments (`-j4`, `--impure` etc)
 are passed to the underlying nix invocation.
 
-##### Tracked files
+#### Tracked files
 
-`nix-direnv` makes a performance tradeoff only considers changes in a limited
-number of files when deciding to update its cache.
+`nix-direnv` makes a performance tradeoff
+and only considers changes in a limited number of files
+when deciding to update its cache.
 
-- for `use nix` this is `~/.direnvrc`, `~/.config/direnv/direnvrc`, `.envrc`, `default.nix` and `shell.nix`
-- for `use flake` this is  `~/.direnvrc`, `~/.config/direnv/direnvrc`, `.envrc`, `flake.nix`, `flake.lock` and `devshell.toml`
+- for `use nix` this is:
+    * `~/.direnvrc`
+    * `~/.config/direnv/direnvrc`
+    * `.envrc`,
+    * A single nix file. In order of preference:
+        + The file argument to `use nix`
+        + `default.nix` if it exists
+        + `shell.nix` if it exists
 
-To add more files to be checked use `nix_direnv_watch_file` like this: `nix_direnv_watch_file your-file.nix`
+- for `use flake` this is:
+    * `~/.direnvrc`
+    * `~/.config/direnv/direnvrc`
+    * `.envrc`
+    * `flake.nix`
+    * `flake.lock`
+    * `devshell.toml` if it exists
+
+To add more files to be checked use `nix_direnv_watch_file` like this
+
+```shell
+$ nix_direnv_watch_file your-file.nix
+```
+
+Or - if you don't mind the overhead (runtime and conceptual) of watching all nix-files:
+
+```shell
+nix_direnv_watch_file $(find . -name "*.nix" -printf '"%p" ')
+```
+
+Note that this will re-execute direnv for any nix change,
+regardless of whether that change is meaningful for the devShell in use.
+
+`nix_direnv_watch_file` must be invoked before either `use flake` or `use nix` to take effect.
 
 ## General direnv tips
 

direnvrc

@@ -303,7 +303,7 @@ use_nix() {
   done
 
   # nixfile may be empty,
-  # but nix_direnv_watch_file checks for existance before adding to watches
+  # but nix_direnv_watch_file checks for existence before adding to watches
   nix_direnv_watch_file "$HOME/.direnvrc" "$HOME/.config/direnv/direnvrc" .envrc "$nixfile"
 
   local need_update=0