treemanifest: optimize treemanifest._walk() to skip directories

treemanifest: optimize treemanifest._walk() to skip directories

This makes treemanifest.walk() not visit submanifests that are known not to
have any matching files. It does this by calling match.visitdir() on
submanifests as it walks.

This change also updates largefiles to be able to work with this new behavior
in treemanifests. It overrides match.visitdir(), the function that dictates
how walk() and matches() skip over directories.

The greatest speed improvements are seen with narrower scopes. For example,
this commit speeds up the following command on the Mozilla repo from 1.14s
to 1.02s:
  hg files -r . dom/apps/

Whereas with a wider scope, dom/, the speed only improves from 1.21s to 1.13s.

As with similar a similar optimization to treemanifest.matches(), this change
will bring out even bigger performance improvements once treemanifests are
loaded lazily. Once that happens, we won't just skip over looking at
submanifests, but we'll skip even loading them.

--- a/hgext/largefiles/overrides.py	Wed Apr 08 22:31:50 2015 -0400
+++ b/hgext/largefiles/overrides.py	Tue Apr 07 15:18:52 2015 -0700
@@ -1274,6 +1274,20 @@
         if not f in notbad:
             origbadfn(f, msg)
     m.bad = lfbadfn
+
+    origvisitdirfn = m.visitdir
+    def lfvisitdirfn(dir):
+        if dir == lfutil.shortname:
+            return True
+        ret = origvisitdirfn(dir)
+        if ret:
+            return ret
+        lf = lfutil.splitstandin(dir)
+        if lf is None:
+            return False
+        return origvisitdirfn(lf)
+    m.visitdir = lfvisitdirfn
+
     for f in ctx.walk(m):
         fp = cmdutil.makefileobj(repo, opts.get('output'), ctx.node(),
                                  pathname=f)

--- a/mercurial/manifest.py	Wed Apr 08 22:31:50 2015 -0400
+++ b/mercurial/manifest.py	Tue Apr 07 15:18:52 2015 -0700
@@ -609,13 +609,6 @@
         '''
         fset = set(match.files())
 
-        # avoid the entire walk if we're only looking for specific files
-        if fset and not match.anypats():
-            if util.all(fn in self for fn in fset):
-                for fn in sorted(fset):
-                    yield fn
-                raise StopIteration
-
         for fn in self._walk(match):
             if fn in fset:
                 # specified pattern is the exact name
@@ -630,8 +623,18 @@
             if not self.hasdir(fn):
                 match.bad(fn, None)
 
-    def _walk(self, match):
-        '''Recursively generates matching file names for walk().'''
+    def _walk(self, match, alldirs=False):
+        '''Recursively generates matching file names for walk().
+
+        Will visit all subdirectories if alldirs is True, otherwise it will
+        only visit subdirectories for which match.visitdir is True.'''
+
+        if not alldirs:
+            # substring to strip trailing slash
+            visit = match.visitdir(self._dir[:-1] or '.')
+            if not visit:
+                return
+            alldirs = (visit == 'all')
 
         # yield this dir's files and walk its submanifests
         for p in sorted(self._dirs.keys() + self._files.keys()):
@@ -640,7 +643,7 @@
                 if match(fullp):
                     yield fullp
             else:
-                for f in self._dirs[p]._walk(match):
+                for f in self._dirs[p]._walk(match, alldirs):
                     yield f
 
     def matches(self, match):