vfs: have tryunlink tell what it did

It is useful in certain circumstances to know whether vfs.tryunlink()
actually removed something or not, be it for logging purposes.

mercurial/util.py

@@ -2610,12 +2610,16 b' def unlinkpath('
             pass
 
 
-def tryunlink(f: bytes) -> None:
-    """Attempt to remove a file, ignoring FileNotFoundError."""
+def tryunlink(f: bytes) -> bool:
+    """Attempt to remove a file, ignoring FileNotFoundError.
+
+    Returns False in case the file did not exit, True otherwise
+    """
     try:
         unlink(f)
+        return True
     except FileNotFoundError:
-        pass
+        return False
 
 
 def makedirs(

mercurial/vfs.py

@@ -303,7 +303,7 b' class abstractvfs:'
 
     def tryunlink(self, path: Optional[bytes] = None):
         """Attempt to remove a file, ignoring missing file errors."""
-        util.tryunlink(self.join(path))
+        return util.tryunlink(self.join(path))
 
     def unlinkpath(
         self, path: Optional[bytes] = None, ignoremissing=False, rmdir=True