watch: add file watching with automatic process restart

Add watching to procman where it benefits projects of all languages
rather than build it into Ruby or Go projects/frameworks.

Syntax: add `# watch: PATTERNS` to Procfile.dev entries:

    web: bundle exec ruby cmd/web.rb  # watch: lib/**/*.rb

On file change matching a pattern, procman sends SIGINT to the process,
waits for exit, and restarts. Changes are debounced (500ms) to avoid
rapid restarts during multi-file saves.

Processes without a watch annotation behave exactly as before.

#4

Co-authored-by: Warp <agent@warp.dev>

Author: croaky

README.md

@@ -60,11 +60,29 @@ running processes, wait 5s, and then send a `SIGKILL` to all remaining processes
 It runs the processes in `Procfile.dev` "as-is";
 It does not load environment variables from `.env` before running.
 
+## File watching
+
+Add `# watch: PATTERNS` to automatically restart a process when files change:
+
+```txt
+web: bundle exec ruby cmd/web.rb  # watch: lib/**/*.rb,ui/**/*.haml
+esbuild: bun run buildwatch
+```
+
+Patterns are relative to the directory containing `Procfile.dev`.
+Glob patterns support `*` (single directory) and `**` (recursive).
+Processes without a watch annotation run without file watching.
+Changes are debounced (500ms) to avoid rapid restarts.
+On change, procman sends SIGINT, waits for the process to exit, then restarts it.
+
 `procman` is distributed via Go source code,
 not via a Homebrew package.
 
-`procman` depends on [github.com/creack/pty](https://github.com/creack/pty/tree/master)
-for a PTY interface.
+`procman` depends on:
+
+- [creack/pty](https://github.com/creack/pty) for PTY interface
+- [fsnotify/fsnotify](https://github.com/fsnotify/fsnotify) for file watching
+- [bmatcuk/doublestar](https://github.com/bmatcuk/doublestar) for glob patterns
 
 ## Developing
 

go.mod

@@ -2,4 +2,10 @@ module github.com/croaky/procman
 
 go 1.25
 
-require github.com/creack/pty v1.1.24
+require (
+	github.com/bmatcuk/doublestar/v4 v4.10.0
+	github.com/creack/pty v1.1.24
+	github.com/fsnotify/fsnotify v1.9.0
+)
+
+require golang.org/x/sys v0.13.0 // indirect

go.sum

@@ -1,2 +1,8 @@
+github.com/bmatcuk/doublestar/v4 v4.10.0 h1:zU9WiOla1YA122oLM6i4EXvGW62DvKZVxIe6TYWexEs=
+github.com/bmatcuk/doublestar/v4 v4.10.0/go.mod h1:xBQ8jztBU6kakFMg+8WGxn0c6z1fTSPVIjEY1Wr7jzc=
 github.com/creack/pty v1.1.24 h1:bJrF4RRfyJnbTJqzRLHzcGaZK1NeM5kTC9jGgovnR1s=
 github.com/creack/pty v1.1.24/go.mod h1:08sCNb52WyoAwi2QDyzUCTgcvVFhUzewun7wtTfvcwE=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=