Read extra ignore file for dev watcher, closes #4406 (#4409)

Co-authored-by: Lucas Nogueira <lucas@tauri.studio>

Author: fehnomenal

.changes/dev-custom-ignore-file.md

@@ -0,0 +1,6 @@
+---
+"cli.rs": patch
+"cli.js": patch
+---
+
+Allow registering a `.gitignore` file to skip watching some project files and directories via the `TAURI_DEV_WATCHER_IGNORE_FILE` environment variable.

tooling/cli/src/dev.rs

@@ -317,6 +317,9 @@ fn lookup<F: FnMut(FileType, PathBuf)>(dir: &Path, mut f: F) {
 
   let mut builder = ignore::WalkBuilder::new(dir);
   let _ = builder.add_ignore(default_gitignore);
+  if let Ok(ignore_file) = std::env::var("TAURI_DEV_WATCHER_IGNORE_FILE") {
+    builder.add_ignore(ignore_file);
+  }
   builder.require_git(false).ignore(false).max_depth(Some(1));
 
   for entry in builder.build().flatten() {