initial copy and modifications from the original py/impl/test/dist and

looponfail code. Now works as its own "xdist" plugin.

xdist/util.py

@@ -0,0 +1,53 @@
+import py
+
+class StatRecorder:
+    def __init__(self, rootdirlist):
+        self.rootdirlist = rootdirlist
+        self.statcache = {}
+        self.check() # snapshot state
+
+    def fil(self, p): 
+        return p.ext in ('.py', '.txt', '.c', '.h')
+    def rec(self, p):
+        return p.check(dotfile=0)
+
+    def waitonchange(self, checkinterval=1.0):
+        while 1:
+            changed = self.check()
+            if changed:
+                return
+            py.std.time.sleep(checkinterval)
+
+    def check(self, removepycfiles=True):
+        changed = False
+        statcache = self.statcache
+        newstat = {}
+        for rootdir in self.rootdirlist:
+            for path in rootdir.visit(self.fil, self.rec):
+                oldstat = statcache.get(path, None)
+                if oldstat is not None:
+                    del statcache[path]
+                try:
+                    newstat[path] = curstat = path.stat()
+                except py.error.ENOENT:
+                    if oldstat:
+                        del statcache[path]
+                        changed = True
+                else:
+                    if oldstat:
+                       if oldstat.mtime != curstat.mtime or \
+                          oldstat.size != curstat.size:
+                            changed = True
+                            py.builtin.print_("# MODIFIED", path)
+                            if removepycfiles and path.ext == ".py":
+                                pycfile = path + "c"
+                                if pycfile.check():
+                                    pycfile.remove()
+                                
+                    else:
+                        changed = True
+        if statcache:
+            changed = True
+        self.statcache = newstat
+        return changed
+