walkchangerevs: make followfilter a top-level class

walkchangerevs: make followfilter a top-level class

The class only depends on the 'repo' variable in the closure, so let's
move the class out of the function and make it explicit that that (the
repo) is all it needs.

--- a/mercurial/cmdutil.py	Thu Mar 19 10:18:05 2015 -0700
+++ b/mercurial/cmdutil.py	Thu Mar 19 09:12:21 2015 -0700
@@ -1669,6 +1669,44 @@
 
     return wanted
 
+class _followfilter(object):
+    def __init__(self, repo, onlyfirst=False):
+        self.repo = repo
+        self.startrev = nullrev
+        self.roots = set()
+        self.onlyfirst = onlyfirst
+
+    def match(self, rev):
+        def realparents(rev):
+            if self.onlyfirst:
+                return self.repo.changelog.parentrevs(rev)[0:1]
+            else:
+                return filter(lambda x: x != nullrev,
+                              self.repo.changelog.parentrevs(rev))
+
+        if self.startrev == nullrev:
+            self.startrev = rev
+            return True
+
+        if rev > self.startrev:
+            # forward: all descendants
+            if not self.roots:
+                self.roots.add(self.startrev)
+            for parent in realparents(rev):
+                if parent in self.roots:
+                    self.roots.add(rev)
+                    return True
+        else:
+            # backwards: all parents
+            if not self.roots:
+                self.roots.update(realparents(self.startrev))
+            if rev in self.roots:
+                self.roots.remove(rev)
+                self.roots.update(realparents(rev))
+                return True
+
+        return False
+
 def walkchangerevs(repo, match, opts, prepare):
     '''Iterate over files and the revs in which they changed.
 
@@ -1757,48 +1795,11 @@
 
         wanted = lazywantedset()
 
-    class followfilter(object):
-        def __init__(self, onlyfirst=False):
-            self.startrev = nullrev
-            self.roots = set()
-            self.onlyfirst = onlyfirst
-
-        def match(self, rev):
-            def realparents(rev):
-                if self.onlyfirst:
-                    return repo.changelog.parentrevs(rev)[0:1]
-                else:
-                    return filter(lambda x: x != nullrev,
-                                  repo.changelog.parentrevs(rev))
-
-            if self.startrev == nullrev:
-                self.startrev = rev
-                return True
-
-            if rev > self.startrev:
-                # forward: all descendants
-                if not self.roots:
-                    self.roots.add(self.startrev)
-                for parent in realparents(rev):
-                    if parent in self.roots:
-                        self.roots.add(rev)
-                        return True
-            else:
-                # backwards: all parents
-                if not self.roots:
-                    self.roots.update(realparents(self.startrev))
-                if rev in self.roots:
-                    self.roots.remove(rev)
-                    self.roots.update(realparents(rev))
-                    return True
-
-            return False
-
     # it might be worthwhile to do this in the iterator if the rev range
     # is descending and the prune args are all within that range
     for rev in opts.get('prune', ()):
         rev = repo[rev].rev()
-        ff = followfilter()
+        ff = _followfilter(repo)
         stop = min(revs[0], revs[-1])
         for x in xrange(rev, stop - 1, -1):
             if ff.match(x):
@@ -1808,7 +1809,7 @@
     # revision range, yielding only revisions in wanted.
     def iterate():
         if follow and not match.files():
-            ff = followfilter(onlyfirst=opts.get('follow_first'))
+            ff = _followfilter(repo, onlyfirst=opts.get('follow_first'))
             def want(rev):
                 return ff.match(rev) and rev in wanted
         else: