inotify: server: new data structure to keep track of changes.

== Rationale for the new structure ==

Current structure was a dictionary tree. One directory was tracked
as a dictionary:
 - keys: file/subdir name
 - values:
    - for a file, the status (a/r/m/...)
    - for a subdir, the directory representing the subdir

It allowed efficient lookups, no matter of the type of the terminal leaf:
    for part in path.split('/'): tree = tree[part]

However, there is no way to represent a directory and a file with the same name
because keys are conflicting in the dictionary. Concrete example:

Initial state:

root dir
 |- foo (file)
 |- bar (file)

# data state is: {'foo': 'n', 'bar': 'n'}

Remove foo:

root dir
 |- bar (file)

# Data becomes {'foo': 'r'} until next commit.

Add foo, as a directory, and foo/barbar file:

root dir
 |- bar (file)
 |-> foo (dir)
  |- barbar (file)

# New state should be represented as:
  {'foo': {'barbar': 'a'}, 'bar': 'n'}
  however, the key "foo" is already used and represents the old file.

The dirstate:
 D foo
 A foo/barbar
cannot be represented, hence the need for a new structure.

== The new structure ==

'directory' class. Represents one directory level.
* Notable attributes:
  Two dictionaries:
   - 'files' Maps filename -> status for the current dir.
   - 'dirs' Maps subdir's name -> directory object representing the subdir
* methods
  - walk(), formerly server.walk
  - lookup(), old server.lookup
  - dir(), old server.dir

This new class allows embedding all the tree walks/lookups in its own class,
instead of having everything mixed together in server.

Incidently, since files and directories are not stored in the same
dictionaries, we are solving the previous key conflict problem.

The small drawback is that lookup operation is a bit more complex:
for a path a/b/c/d/e we have to check twice the leaf, if e is a directory or a
file.

hgext/inotify/server.py

@@ -201,6 +201,92 b' def eventaction(code):'
         return wrapper
     return decorator
 
+class directory(object):
+    """
+    Representing a directory
+
+    * path is the relative path from repo root to this directory
+    * files is a dict listing the files in this directory
+        - keys are file names
+        - values are file status
+    * dirs is a dict listing the subdirectories
+        - key are subdirectories names
+        - values are directory objects
+    """
+    def __init__(self, relpath=''):
+        self.path = relpath
+        self.files = {}
+        self.dirs = {}
+
+    def dir(self, relpath):
+        """
+        Returns the directory contained at the relative path relpath.
+        Creates the intermediate directories if necessary.
+        """
+        if not relpath:
+            return self
+        l = relpath.split('/')
+        ret = self
+        while l:
+            next = l.pop(0)
+            try:
+                ret = ret.dirs[next]
+            except KeyError:
+                d = directory(join(ret.path, next))
+                ret.dirs[next] = d
+                ret = d
+        return ret
+
+    def walk(self, states):
+        """
+        yield (filename, status) pairs for items in the trees
+        that have status in states.
+        filenames are relative to the repo root
+        """
+        for file, st in self.files.iteritems():
+            if st in states:
+                yield join(self.path, file), st
+        for dir in self.dirs.itervalues():
+            for e in dir.walk(states):
+                yield e
+
+    def lookup(self, states, path):
+        """
+        yield root-relative filenames that match path, and whose
+        status are in states:
+        * if path is a file, yield path
+        * if path is a directory, yield directory files
+        * if path is not tracked, yield nothing
+        """
+        if path[-1] == '/':
+            path = path[:-1]
+
+        paths = path.split('/')
+
+        # we need to check separately for last node
+        last = paths.pop()
+
+        tree = self
+        try:
+            for dir in paths:
+                tree = tree.dirs[dir]
+        except KeyError:
+            # path is not tracked
+            return
+
+        try:
+            # if path is a directory, walk it
+            for file, st in tree.dirs[last].walk(states):
+                yield file
+        except KeyError:
+            try:
+                if tree.files[last] in states:
+                    # path is a file
+                    yield path
+            except KeyError:
+                # path is not tracked
+                pass
+
 class repowatcher(pollable):
     """
     Watches inotify events
@@ -231,9 +317,9 b' class repowatcher(pollable):'
         self.threshold = watcher.threshold(self.watcher)
         self.fileno = self.watcher.fileno
 
-        self.tree = {}
+        self.tree = directory()
         self.statcache = {}
-        self.statustrees = dict([(s, {}) for s in self.statuskeys])
+        self.statustrees = dict([(s, directory()) for s in self.statuskeys])
 
         self.last_event = None
 
@@ -288,23 +374,6 b' class repowatcher(pollable):'
         self.add_watch(self.repo.path, inotify.IN_DELETE)
         self.check_dirstate()
 
-    def dir(self, tree, path):
-        if path:
-            for name in path.split('/'):
-                tree = tree.setdefault(name, {})
-        return tree
-
-    def lookup(self, path, tree):
-        if path:
-            try:
-                for name in path.split('/'):
-                    tree = tree[name]
-            except KeyError:
-                return 'x'
-            except TypeError:
-                return 'd'
-        return tree
-
     def filestatus(self, fn, st):
         try:
             type_, mode, size, time = self.repo.dirstate._map[fn][:4]
@@ -350,53 +419,47 b' class repowatcher(pollable):'
 
     def _updatestatus(self, wfn, newstatus):
         '''
-        Update the stored status of a file or directory.
+        Update the stored status of a file.
 
         newstatus: - char in (statuskeys + 'ni'), new status to apply.
                    - or None, to stop tracking wfn
         '''
         root, fn = split(wfn)
-        d = self.dir(self.tree, root)
+        d = self.tree.dir(root)
 
-        oldstatus = d.get(fn)
+        oldstatus = d.files.get(fn)
         # oldstatus can be either:
         # - None : fn is new
         # - a char in statuskeys: fn is a (tracked) file
-        # - a dict: fn is a directory
-        isdir = isinstance(oldstatus, dict)
 
         if self.ui.debugflag and oldstatus != newstatus:
-            if isdir:
-                self.ui.note(_('status: %r dir(%d) -> %s\n') %
-                             (wfn, len(oldstatus), newstatus))
-            else:
-                self.ui.note(_('status: %r %s -> %s\n') %
+            self.ui.note(_('status: %r %s -> %s\n') %
                              (wfn, oldstatus, newstatus))
-        if not isdir:
-            if oldstatus and oldstatus in self.statuskeys \
-                and oldstatus != newstatus:
-                del self.dir(self.statustrees[oldstatus], root)[fn]
-            if newstatus and newstatus != 'i':
-                d[fn] = newstatus
-                if newstatus in self.statuskeys:
-                    dd = self.dir(self.statustrees[newstatus], root)
-                    if oldstatus != newstatus or fn not in dd:
-                        dd[fn] = newstatus
-            else:
-                d.pop(fn, None)
+
+        if oldstatus and oldstatus in self.statuskeys \
+            and oldstatus != newstatus:
+            del self.statustrees[oldstatus].dir(root).files[fn]
+        if newstatus and newstatus != 'i':
+            d.files[fn] = newstatus
+            if newstatus in self.statuskeys:
+                dd = self.statustrees[newstatus].dir(root)
+                if oldstatus != newstatus or fn not in dd.files:
+                    dd.files[fn] = newstatus
+        else:
+            d.files.pop(fn, None)
 
 
     def check_deleted(self, key):
         # Files that had been deleted but were present in the dirstate
         # may have vanished from the dirstate; we must clean them up.
         nuke = []
-        for wfn, ignore in self.walk(key, self.statustrees[key]):
+        for wfn, ignore in self.statustrees[key].walk(key):
             if wfn not in self.repo.dirstate:
                 nuke.append(wfn)
         for wfn in nuke:
             root, fn = split(wfn)
-            del self.dir(self.statustrees[key], root)[fn]
-            del self.dir(self.tree, root)[fn]
+            del self.statustrees[key].dir(root).files[fn]
+            del self.tree.dir(root).files[fn]
 
     def scan(self, topdir=''):
         ds = self.repo.dirstate._map.copy()
@@ -438,18 +501,6 b' class repowatcher(pollable):'
         self.scan()
         self.ui.note(_('%s end dirstate reload\n') % self.event_time())
 
-    def walk(self, states, tree, prefix=''):
-        # This is the "inner loop" when talking to the client.
-
-        for name, val in tree.iteritems():
-            path = join(prefix, name)
-            try:
-                if val in states:
-                    yield path, val
-            except TypeError:
-                for p in self.walk(states, val, path):
-                    yield p
-
     def update_hgignore(self):
         # An update of the ignore file can potentially change the
         # states of all unknown and ignored files.
@@ -537,9 +588,10 b' class repowatcher(pollable):'
                          (self.event_time(), wpath))
 
         if evt.mask & inotify.IN_ISDIR:
-            tree = self.dir(self.tree, wpath).copy()
-            for wfn, ignore in self.walk('?', tree):
-                self.deletefile(join(wpath, wfn), '?')
+            tree = self.tree.dir(wpath)
+            todelete = [wfn for wfn, ignore in tree.walk('?')]
+            for fn in todelete:
+                self.deletefile(fn, '?')
             self.scan(wpath)
         else:
             self.deleted(wpath)
@@ -669,18 +721,13 b' class server(pollable):'
 
         if not names:
             def genresult(states, tree):
-                for fn, state in self.repowatcher.walk(states, tree):
+                for fn, state in tree.walk(states):
                     yield fn
         else:
             def genresult(states, tree):
                 for fn in names:
-                    l = self.repowatcher.lookup(fn, tree)
-                    try:
-                        if l in states:
-                            yield fn
-                    except TypeError:
-                        for f, s in self.repowatcher.walk(states, l, fn):
-                            yield f
+                    for f in tree.lookup(states, fn):
+                        yield f
 
         return ['\0'.join(r) for r in [
             genresult('l', self.repowatcher.statustrees['l']),