grep: extract public function to register file to be skipped

The main grep loop will be extracted to a searcher method, but this skipping
condition depends on the result of display() function.

mercurial/commands.py

@@ -3549,9 +3549,7 b' def grep(ui, repo, pattern, *pats, **opt'
                 r = display(fm, fn, ctx, pstates, states)
                 found = found or r
                 if r and not diff and not all_files:
-                    skip.add(fn)
-                    if copy:
-                        skip.add(copy)
+                    searcher.skipfile(fn, rev)
         del revfiles[rev]
         # We will keep the matches dict for the duration of the window
         # clear the matches dict once the window is over

mercurial/grep.py

@@ -107,6 +107,14 b' class grepsearcher(object):'
         self._skip = set()
         self._revfiles = {}
 
+    def skipfile(self, fn, rev):
+        """Exclude the given file (and the copy at the specified revision)
+        from future search"""
+        copy = self._copies.get(rev, {}).get(fn)
+        self._skip.add(fn)
+        if copy:
+            self._skip.add(copy)
+
     def _grepbody(self, fn, rev, body):
         self._matches[rev].setdefault(fn, [])
         m = self._matches[rev][fn]