Optimize dirstate walking

This generally cuts the time for hg status/diff in half, from 2s down to 1s.
The main parts I'm trying to optimize are:

1) os.walk stats every file.  dirstate.changes then stats every file again.

2) os.walk yields every file and subdir to dirstate.traverse who yields every
file and everything in the dirstate map.  dirstate.walk then
filters this mass and yields every file to the caller.  There should be
fewer steps in here, and fewer duplicate strings yielded.

3) dirstate.walk runs util.unique on the results from dirstate.traverse,
even though it is also passing things through dirstate.seen to look for
duplicates.

I've turned os.walk into something hg specific that takes all the dirstate
ignore and matching rules into account.  The new function also takes an
function arg (statmatch()) the caller supplies to help filter out
files it doesn't care about.  dirstate.changes uses this to update state
for each file, avoiding the second stat call.

dirstate.walk is changed to turn the match function it is passed into
a statmatch function.  The only real difference is that a statmatch
function takes the stat data as a second parameter.  It now calls
dirstate.walkhelper, who requires a statmatch function to be passed.

This fails test-walk, but right now I think this is from a sorting error
fixed by this patch.

Index: crew/mercurial/dirstate.py
===================================================================

mercurial/dirstate.py

@@ -22,6 +22,7 b' class dirstate:'
         self.pl = None
         self.copies = {}
         self.ignorefunc = None
+        self.blockignore = False
 
     def wjoin(self, f):
         return os.path.join(self.root, f)
@@ -32,6 +33,8 b' class dirstate:'
         return cwd[len(self.root) + 1:]
 
     def ignore(self, f):
+        if self.blockignore:
+            return False
         if not self.ignorefunc:
             bigpat = []
             try:
@@ -214,11 +217,55 b' class dirstate:'
         elif not dc:
             dc = self.filterfiles(files)
 
+        def statmatch(file, stat):
+            if file not in dc and self.ignore(file):
+                return False
+            return match(file)
+        return self.walkhelper(files=files, statmatch=statmatch, dc=dc)
+
+    # walk recursively through the directory tree, finding all files
+    # matched by the statmatch function
+    # 
+    # results are yielded in a tuple (src, filename), where src is one of:
+    # 'f' the file was found in the directory tree
+    # 'm' the file was only in the dirstate and not in the tree
+    #
+    # dc is an optional arg for the current dirstate.  dc is not modified
+    # directly by this function, but might be modified by your statmatch call.
+    #
+    def walkhelper(self, files, statmatch, dc):
+        # recursion free walker, faster than os.walk.
+        def findfiles(s):
+            retfiles = []
+            work = [s]
+            while work:
+                top = work.pop()
+                names = os.listdir(top)
+                names.sort()
+                # nd is the top of the repository dir tree
+                nd = util.normpath(top[len(self.root) + 1:])
+                if nd == '.': nd = ''
+                for f in names:
+                    np = os.path.join(nd, f)
+                    if seen(np):
+                        continue
+                    p = os.path.join(top, f)
+                    st = os.stat(p)
+                    if stat.S_ISDIR(st.st_mode):
+                        ds = os.path.join(nd, f +'/')
+                        if statmatch(ds, st):
+                            work.append(p)
+                    else:
+                        if statmatch(np, st):
+                            yield np
+
         known = {'.hg': 1}
         def seen(fn):
             if fn in known: return True
             known[fn] = 1
-        def traverse():
+
+        # step one, find all files that match our criteria
+        files.sort()
             for ff in util.unique(files):
                 f = os.path.join(self.root, ff)
                 try:
@@ -229,23 +276,20 b' class dirstate:'
                         inst.strerror))
                     continue
                 if stat.S_ISDIR(st.st_mode):
-                    for dir, subdirs, fl in os.walk(f):
-                        d = dir[len(self.root) + 1:]
-                        nd = util.normpath(d)
-                        if nd == '.': nd = ''
-                        if seen(nd):
-                            subdirs[:] = []
+                sorted = [ x for x in findfiles(f) ]
+                sorted.sort()
+                for fl in sorted:
+                    yield 'f', fl
+            elif stat.S_ISREG(st.st_mode):
+                ff = util.normpath(ff)
+                if seen(ff):
                             continue
-                        for sd in subdirs:
-                            ds = os.path.join(nd, sd +'/')
-                            if self.ignore(ds) or not match(ds):
-                                subdirs.remove(sd)
-                        subdirs.sort()
-                        fl.sort()
-                        for fn in fl:
-                            fn = util.pconvert(os.path.join(d, fn))
-                            yield 'f', fn
-                elif stat.S_ISREG(st.st_mode):
+                found = False
+                self.blockignore = True
+                if statmatch(ff, st):
+                    found = True
+                self.blockignore = False
+                if found:
                     yield 'f', ff
                 else:
                     kind = 'unknown'
@@ -258,54 +302,68 b' class dirstate:'
                         util.pathto(self.getcwd(), ff),
                         kind))
 
+        # step two run through anything left in the dc hash and yield
+        # if we haven't already seen it
             ks = dc.keys()
             ks.sort()
             for k in ks:
+            if not seen(k) and (statmatch(k, None)):
                 yield 'm', k
 
-        # yield only files that match: all in dirstate, others only if
-        # not in .hgignore
-
-        for src, fn in util.unique(traverse()):
-            fn = util.normpath(fn)
-            if seen(fn): continue
-            if fn not in dc and self.ignore(fn):
-                continue
-            if match(fn):
-                yield src, fn
-
     def changes(self, files=None, match=util.always):
         self.read()
         if not files:
+            files = [self.root]
             dc = self.map.copy()
         else:
             dc = self.filterfiles(files)
         lookup, modified, added, unknown = [], [], [], []
         removed, deleted = [], []
 
-        for src, fn in self.walk(files, match, dc=dc):
-            try:
-                s = os.stat(os.path.join(self.root, fn))
-            except OSError:
-                continue
+        # statmatch function to eliminate entries from the dirstate copy
+        # and put files into the appropriate array.  This gets passed
+        # to the walking code
+        def statmatch(fn, s):
+            def checkappend(l, fn):
+                if match is util.always or match(fn):
+                    l.append(fn)
+                   
+            if not s or stat.S_ISDIR(s.st_mode):
+                return self.ignore(fn) and False or match(fn)
+
             if not stat.S_ISREG(s.st_mode):
-                continue
-            c = dc.get(fn)
+                return False
+            c = dc.pop(fn, None)
             if c:
-                del dc[fn]
-                if c[0] == 'm':
-                    modified.append(fn)
-                elif c[0] == 'a':
-                    added.append(fn)
-                elif c[0] == 'r':
+                type, mode, size, time = c
+                # check the common case first
+                if type == 'n':
+                    if size != s.st_size or (mode ^ s.st_mode) & 0100:
+                        checkappend(modified, fn)
+                    elif time != s.st_mtime:
+                        checkappend(lookup, fn)
+                elif type == 'm':
+                    checkappend(modified, fn)
+                elif type == 'a':
+                    checkappend(added, fn)
+                elif type == 'r':
+                    checkappend(unknown, fn)
+            else:
+                if not self.ignore(fn) and match(fn):
                     unknown.append(fn)
-                elif c[2] != s.st_size or (c[1] ^ s.st_mode) & 0100:
-                    modified.append(fn)
-                elif c[3] != s.st_mtime:
-                    lookup.append(fn)
-            else:
-                unknown.append(fn)
+            # return false because we've already handled all cases above.
+            # there's no need for the walking code to process the file
+            # any further.
+            return False
 
+        # because our statmatch always returns false, self.walk will only
+        # return files in the dirstate map that are not present in the FS.
+        # But, we still need to iterate through the results to force the
+        # walk to complete
+        for src, fn in self.walkhelper(files, statmatch, dc):
+            pass
+
+        # anything left in dc didn't exist in the filesystem
         for fn, c in [(fn, c) for fn, c in dc.items() if match(fn)]:
             if c[0] == 'r':
                 removed.append(fn)