hg update: fix clobbering files when going backwards

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Hash: SHA1

hg update: fix clobbering files when going backwards

spotted by Andrew Thompson

manifest hash: 0cfc2d189a395fb8761391d9918864034aa7a9b8
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Version: GnuPG v1.4.0 (GNU/Linux)

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mercurial/hg.py

@@ -1,1261 +1,1264 b''
 # hg.py - repository classes for mercurial
 #
 # Copyright 2005 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
 import sys, struct, os
 from revlog import *
 from demandload import *
 demandload(globals(), "re lock urllib urllib2 transaction time socket")
 demandload(globals(), "tempfile byterange difflib")
 
 def is_exec(f):
     return (os.stat(f).st_mode & 0100 != 0)
 
 def set_exec(f, mode):
     s = os.stat(f).st_mode
     if (s & 0100 != 0) == mode:
         return
     os.chmod(f, s & 0666 | (mode * 0111))
 
 class filelog(revlog):
     def __init__(self, opener, path):
         revlog.__init__(self, opener,
                         os.path.join("data", path + ".i"),
                         os.path.join("data", path + ".d"))
 
     def read(self, node):
         return self.revision(node)
     def add(self, text, transaction, link, p1=None, p2=None):
         return self.addrevision(text, transaction, link, p1, p2)
 
     def annotate(self, node):
 
         def decorate(text, rev):
             return [(rev, l) for l in text.splitlines(1)]
 
         def strip(annotation):
             return [e[1] for e in annotation]
 
         def pair(parent, child):
             new = []
             sm = difflib.SequenceMatcher(None, strip(parent), strip(child))
             for o, m, n, s, t in sm.get_opcodes():
                 if o == 'equal':
                     new += parent[m:n]
                 else:
                     new += child[s:t]
             return new
 
         # find all ancestors
         needed = {node:1}
         visit = [node]
         while visit:
             n = visit.pop(0)
             for p in self.parents(n):
                 if p not in needed:
                     needed[p] = 1
                     visit.append(p)
                 else:
                     # count how many times we'll use this
                     needed[p] += 1
 
         # sort by revision which is a topological order
         visit = needed.keys()
         visit = [ (self.rev(n), n) for n in visit ]
         visit.sort()
         visit = [ p[1] for p in visit ]
         hist = {}
 
         for n in visit:
             curr = decorate(self.read(n), self.linkrev(n))
             for p in self.parents(n):
                 if p != nullid:
                     curr = pair(hist[p], curr)
                     # trim the history of unneeded revs
                     needed[p] -= 1
                     if not needed[p]:
                         del hist[p]
             hist[n] = curr
 
         return hist[n]
 
 class manifest(revlog):
     def __init__(self, opener):
         self.mapcache = None
         self.listcache = None
         self.addlist = None
         revlog.__init__(self, opener, "00manifest.i", "00manifest.d")
 
     def read(self, node):
         if self.mapcache and self.mapcache[0] == node:
             return self.mapcache[1].copy()
         text = self.revision(node)
         map = {}
         flag = {}
         self.listcache = (text, text.splitlines(1))
         for l in self.listcache[1]:
             (f, n) = l.split('\0')
             map[f] = bin(n[:40])
             flag[f] = (n[40:-1] == "x")
         self.mapcache = (node, map, flag)
         return map
 
     def readflags(self, node):
         if self.mapcache or self.mapcache[0] != node:
             self.read(node)
         return self.mapcache[2]
 
     def diff(self, a, b):
         # this is sneaky, as we're not actually using a and b
         if self.listcache and self.addlist and self.listcache[0] == a:
             d = mdiff.diff(self.listcache[1], self.addlist, 1)
             if mdiff.patch(a, d) != b:
                 sys.stderr.write("*** sortdiff failed, falling back ***\n")
                 return mdiff.textdiff(a, b)
             return d
         else:
             return mdiff.textdiff(a, b)
 
     def add(self, map, flags, transaction, link, p1=None, p2=None):
         files = map.keys()
         files.sort()
 
         self.addlist = ["%s\000%s%s\n" %
                         (f, hex(map[f]), flags[f] and "x" or '')
                         for f in files]
         text = "".join(self.addlist)
 
         n = self.addrevision(text, transaction, link, p1, p2)
         self.mapcache = (n, map)
         self.listcache = (text, self.addlist)
         self.addlist = None
 
         return n
 
 class changelog(revlog):
     def __init__(self, opener):
         revlog.__init__(self, opener, "00changelog.i", "00changelog.d")
 
     def extract(self, text):
         if not text:
             return (nullid, "", "0", [], "")
         last = text.index("\n\n")
         desc = text[last + 2:]
         l = text[:last].splitlines()
         manifest = bin(l[0])
         user = l[1]
         date = l[2]
         files = l[3:]
         return (manifest, user, date, files, desc)
 
     def read(self, node):
         return self.extract(self.revision(node))
 
     def add(self, manifest, list, desc, transaction, p1=None, p2=None,
                   user=None, date=None):
         user = (user or
                 os.environ.get("HGUSER") or
                 os.environ.get("EMAIL") or
                 os.environ.get("LOGNAME", "unknown") + '@' + socket.getfqdn())
         date = date or "%d %d" % (time.time(), time.timezone)
         list.sort()
         l = [hex(manifest), user, date] + list + ["", desc]
         text = "\n".join(l)
         return self.addrevision(text, transaction, self.count(), p1, p2)
 
 class dirstate:
     def __init__(self, opener, ui, root):
         self.opener = opener
         self.root = root
         self.dirty = 0
         self.ui = ui
         self.map = None
         self.pl = None
 
     def __del__(self):
         if self.dirty:
             self.write()
 
     def __getitem__(self, key):
         try:
             return self.map[key]
         except TypeError:
             self.read()
             return self[key]
 
     def __contains__(self, key):
         if not self.map: self.read()
         return key in self.map
 
     def parents(self):
         if not self.pl:
             self.read()
         return self.pl
 
     def setparents(self, p1, p2 = nullid):
         self.dirty = 1
         self.pl = p1, p2
 
     def state(self, key):
         try:
             return self[key][0]
         except KeyError:
             return "?"
 
     def read(self):
         if self.map is not None: return self.map
 
         self.map = {}
         self.pl = [nullid, nullid]
         try:
             st = self.opener("dirstate").read()
         except: return
 
         self.pl = [st[:20], st[20: 40]]
 
         pos = 40
         while pos < len(st):
             e = struct.unpack(">cllll", st[pos:pos+17])
             l = e[4]
             pos += 17
             f = st[pos:pos + l]
             self.map[f] = e[:4]
             pos += l
         
     def update(self, files, state):
         ''' current states:
         n  normal
         m  needs merging
         r  marked for removal
         a  marked for addition'''
 
         if not files: return
         self.read()
         self.dirty = 1
         for f in files:
             if state == "r":
                 self.map[f] = ('r', 0, 0, 0)
             else:
                 s = os.stat(os.path.join(self.root, f))
                 self.map[f] = (state, s.st_mode, s.st_size, s.st_mtime)
 
     def forget(self, files):
         if not files: return
         self.read()
         self.dirty = 1
         for f in files:
             try:
                 del self.map[f]
             except KeyError:
                 self.ui.warn("not in dirstate: %s!\n" % f)
                 pass
 
     def clear(self):
         self.map = {}
         self.dirty = 1
 
     def write(self):
         st = self.opener("dirstate", "w")
         st.write("".join(self.pl))
         for f, e in self.map.items():
             e = struct.pack(">cllll", e[0], e[1], e[2], e[3], len(f))
             st.write(e + f)
         self.dirty = 0
 
     def copy(self):
         self.read()
         return self.map.copy()
 
 # used to avoid circular references so destructors work
 def opener(base):
     p = base
     def o(path, mode="r"):
         if p[:7] == "http://":
             f = os.path.join(p, urllib.quote(path))
             return httprangereader(f)
 
         f = os.path.join(p, path)
 
         mode += "b" # for that other OS
 
         if mode[0] != "r":
             try:
                 s = os.stat(f)
             except OSError:
                 d = os.path.dirname(f)
                 if not os.path.isdir(d):
                     os.makedirs(d)
             else:
                 if s.st_nlink > 1:
                     file(f + ".tmp", "w").write(file(f).read())
                     os.rename(f+".tmp", f)
 
         return file(f, mode)
 
     return o
 
 class localrepository:
     def __init__(self, ui, path=None, create=0):
         self.remote = 0
         if path and path[:7] == "http://":
             self.remote = 1
             self.path = path
         else:
             if not path:
                 p = os.getcwd()
                 while not os.path.isdir(os.path.join(p, ".hg")):
                     p = os.path.dirname(p)
                     if p == "/": raise "No repo found"
                 path = p
             self.path = os.path.join(path, ".hg")
 
         self.root = path
         self.ui = ui
 
         if create:
             os.mkdir(self.path)  
             os.mkdir(self.join("data"))
 
         self.opener = opener(self.path)
         self.wopener = opener(self.root)
         self.manifest = manifest(self.opener)
         self.changelog = changelog(self.opener)
         self.ignorelist = None
         self.tags = None
 
         if not self.remote:
             self.dirstate = dirstate(self.opener, ui, self.root)
 
     def ignore(self, f):
         if self.ignorelist is None:
             self.ignorelist = []
             try:
                 l = self.wfile(".hgignore")
                 for pat in l:
                     if pat != "\n":
                         self.ignorelist.append(re.compile(pat[:-1]))
             except IOError: pass
         for pat in self.ignorelist:
             if pat.search(f): return True
         return False
 
     def lookup(self, key):
         if self.tags is None:
             self.tags = {}
             try:
                 # read each head of the tags file, ending with the tip
                 # and add each tag found to the map, with "newer" ones
                 # taking precedence
                 fl = self.file(".hgtags")
                 h = fl.heads()
                 h.reverse()
                 for r in h:
                     for l in fl.revision(r).splitlines():
                         if l:
                             n, k = l.split(" ")
                             self.tags[k] = bin(n)
             except KeyError: pass
         try:
             return self.tags[key]
         except KeyError:
             return self.changelog.lookup(key)
 
     def join(self, f):
         return os.path.join(self.path, f)
 
     def wjoin(self, f):
         return os.path.join(self.root, f)
 
     def file(self, f):
         if f[0] == '/': f = f[1:]
         return filelog(self.opener, f)
 
     def wfile(self, f, mode='r'):
         return self.wopener(f, mode)
 
     def transaction(self):
         # save dirstate for undo
         try:
             ds = self.opener("dirstate").read()
         except IOError:
             ds = ""
         self.opener("undo.dirstate", "w").write(ds)
         
         return transaction.transaction(self.opener, self.join("journal"),
                                        self.join("undo"))
 
     def recover(self):
         lock = self.lock()
         if os.path.exists(self.join("recover")):
             self.ui.status("attempting to rollback interrupted transaction\n")
             return transaction.rollback(self.opener, self.join("recover"))
         else:
             self.ui.warn("no interrupted transaction available\n")
 
     def undo(self):
         lock = self.lock()
         if os.path.exists(self.join("undo")):
             self.ui.status("attempting to rollback last transaction\n")
             transaction.rollback(self.opener, self.join("undo"))
             self.dirstate = None
             os.rename(self.join("undo.dirstate"), self.join("dirstate"))
             self.dirstate = dirstate(self.opener, self.ui, self.root)
         else:
             self.ui.warn("no undo information available\n")
 
     def lock(self, wait = 1):
         try:
             return lock.lock(self.join("lock"), 0)
         except lock.LockHeld, inst:
             if wait:
                 self.ui.warn("waiting for lock held by %s\n" % inst.args[0])
                 return lock.lock(self.join("lock"), wait)
             raise inst
 
     def rawcommit(self, files, text, user, date, p1=None, p2=None):
         p1 = p1 or self.dirstate.parents()[0] or nullid
         p2 = p2 or self.dirstate.parents()[1] or nullid
         pchange = self.changelog.read(p1)
         pmmap = self.manifest.read(pchange[0])
         tr = self.transaction()
         mmap = {}
         linkrev = self.changelog.count()
         for f in files:
             try:
                 t = file(f).read()
             except IOError:
                 self.ui.warn("Read file %s error, skipped\n" % f)
                 continue
             r = self.file(f)
             # FIXME - need to find both parents properly
             prev = pmmap.get(f, nullid)
             mmap[f] = r.add(t, tr, linkrev, prev)
 
         mnode = self.manifest.add(mmap, tr, linkrev, pchange[0])
         n = self.changelog.add(mnode, files, text, tr, p1, p2, user ,date, )
         tr.close()
         self.dirstate.setparents(p1, p2)
         self.dirstate.clear()
         self.dirstate.update(mmap.keys(), "n")
 
     def commit(self, files = None, text = ""):
         commit = []
         remove = []
         if files:
             for f in files:
                 s = self.dirstate.state(f)
                 if s in 'nmai':
                     commit.append(f)
                 elif s == 'r':
                     remove.append(f)
                 else:
                     self.ui.warn("%s not tracked!\n" % f)
         else:
             (c, a, d, u) = self.diffdir(self.root)
             commit = c + a
             remove = d
 
         if not commit and not remove:
             self.ui.status("nothing changed\n")
             return
 
         p1, p2 = self.dirstate.parents()
         c1 = self.changelog.read(p1)
         c2 = self.changelog.read(p2)
         m1 = self.manifest.read(c1[0])
         mf1 = self.manifest.readflags(c1[0])
         m2 = self.manifest.read(c2[0])
         lock = self.lock()
         tr = self.transaction()
 
         # check in files
         new = {}
         linkrev = self.changelog.count()
         commit.sort()
         for f in commit:
             self.ui.note(f + "\n")
             try:
                 fp = self.wjoin(f)
                 mf1[f] = is_exec(fp)
                 t = file(fp).read()
             except IOError:
                 self.warn("trouble committing %s!\n" % f)
                 raise
 
             r = self.file(f)
             fp1 = m1.get(f, nullid)
             fp2 = m2.get(f, nullid)
             new[f] = r.add(t, tr, linkrev, fp1, fp2)
 
         # update manifest
         m1.update(new)
         for f in remove: del m1[f]
         mn = self.manifest.add(m1, mf1, tr, linkrev, c1[0], c2[0])
 
         # add changeset
         new = new.keys()
         new.sort()
 
         if not text:
             edittext = "\n" + "HG: manifest hash %s\n" % hex(mn)
             edittext += "".join(["HG: changed %s\n" % f for f in new])
             edittext += "".join(["HG: removed %s\n" % f for f in remove])
             edittext = self.ui.edit(edittext)
             if not edittext.rstrip():
                 return 1
             text = edittext
 
         n = self.changelog.add(mn, new, text, tr, p1, p2)
         tr.close()
 
         self.dirstate.setparents(n)
         self.dirstate.update(new, "n")
         self.dirstate.forget(remove)
 
     def diffdir(self, path, changeset = None):
         changed = []
         added = []
         unknown = []
         mf = {}
 
         if changeset:
             change = self.changelog.read(changeset)
             mf = self.manifest.read(change[0])
             dc = dict.fromkeys(mf)
         else:
             changeset = self.dirstate.parents()[0]
             change = self.changelog.read(changeset)
             mf = self.manifest.read(change[0])
             dc = self.dirstate.copy()
 
         def fcmp(fn):
             t1 = self.wfile(fn).read()
             t2 = self.file(fn).revision(mf[fn])
             return cmp(t1, t2)
 
         for dir, subdirs, files in os.walk(self.root):
             d = dir[len(self.root)+1:]
             if ".hg" in subdirs: subdirs.remove(".hg")
             
             for f in files:
                 fn = os.path.join(d, f)
                 try: s = os.stat(os.path.join(self.root, fn))
                 except: continue
                 if fn in dc:
                     c = dc[fn]
                     del dc[fn]
                     if not c:
                         if fcmp(fn):
                             changed.append(fn)
                     elif c[0] == 'm':
                         changed.append(fn)
                     elif c[0] == 'a':
                         added.append(fn)
                     elif c[0] == 'r':
                         unknown.append(fn)
                     elif c[2] != s.st_size or (c[1] ^ s.st_mode) & 0100:
                         changed.append(fn)
                     elif c[1] != s.st_mode or c[3] != s.st_mtime:
                         if fcmp(fn):
                             changed.append(fn)
                 else:
                     if self.ignore(fn): continue
                     unknown.append(fn)
 
         deleted = dc.keys()
         deleted.sort()
 
         return (changed, added, deleted, unknown)
 
     def diffrevs(self, node1, node2):
         changed, added = [], []
 
         change = self.changelog.read(node1)
         mf1 = self.manifest.read(change[0])
         change = self.changelog.read(node2)
         mf2 = self.manifest.read(change[0])
 
         for fn in mf2:
             if mf1.has_key(fn):
                 if mf1[fn] != mf2[fn]:
                     changed.append(fn)
                 del mf1[fn]
             else:
                 added.append(fn)
                 
         deleted = mf1.keys()
         deleted.sort()
     
         return (changed, added, deleted)
 
     def add(self, list):
         for f in list:
             p = self.wjoin(f)
             if not os.path.isfile(p):
                 self.ui.warn("%s does not exist!\n" % f)
             elif self.dirstate.state(f) == 'n':
                 self.ui.warn("%s already tracked!\n" % f)
             else:
                 self.dirstate.update([f], "a")
 
     def forget(self, list):
         for f in list:
             if self.dirstate.state(f) not in 'ai':
                 self.ui.warn("%s not added!\n" % f)
             else:
                 self.dirstate.forget([f])
 
     def remove(self, list):
         for f in list:
             p = self.wjoin(f)
             if os.path.isfile(p):
                 self.ui.warn("%s still exists!\n" % f)
             elif f not in self.dirstate:
                 self.ui.warn("%s not tracked!\n" % f)
             else:
                 self.dirstate.update([f], "r")
 
     def heads(self):
         return self.changelog.heads()
 
     def branches(self, nodes):
         if not nodes: nodes = [self.changelog.tip()]
         b = []
         for n in nodes:
             t = n
             while n:
                 p = self.changelog.parents(n)
                 if p[1] != nullid or p[0] == nullid:
                     b.append((t, n, p[0], p[1]))
                     break
                 n = p[0]
         return b
 
     def between(self, pairs):
         r = []
 
         for top, bottom in pairs:
             n, l, i = top, [], 0
             f = 1
 
             while n != bottom:
                 p = self.changelog.parents(n)[0]
                 if i == f:
                     l.append(n) 
                     f = f * 2
                 n = p
                 i += 1
 
             r.append(l)
 
         return r
 
     def newer(self, nodes):
         m = {}
         nl = []
         pm = {}
         cl = self.changelog
         t = l = cl.count()
 
         # find the lowest numbered node
         for n in nodes:
             l = min(l, cl.rev(n))
             m[n] = 1
 
         for i in xrange(l, t):
             n = cl.node(i)
             if n in m: # explicitly listed
                 pm[n] = 1
                 nl.append(n)
                 continue
             for p in cl.parents(n):
                 if p in pm: # parent listed
                     pm[n] = 1
                     nl.append(n)
                     break
 
         return nl
 
     def getchangegroup(self, remote):
         m = self.changelog.nodemap
         search = []
         fetch = []
         seen = {}
         seenbranch = {}
 
         # if we have an empty repo, fetch everything
         if self.changelog.tip() == nullid:
             self.ui.status("requesting all changes\n")
             return remote.changegroup([nullid])
 
         # otherwise, assume we're closer to the tip than the root
         self.ui.status("searching for changes\n")
         heads = remote.heads()
         unknown = []
         for h in heads:
             if h not in m:
                 unknown.append(h)
 
         if not unknown:
             self.ui.status("nothing to do!\n")
             return None
             
         unknown = remote.branches(unknown)
         while unknown:
             n = unknown.pop(0)
             seen[n[0]] = 1
             
             self.ui.debug("examining %s:%s\n" % (short(n[0]), short(n[1])))
             if n == nullid: break
             if n in seenbranch:
                 self.ui.debug("branch already found\n")
                 continue
             if n[1] and n[1] in m: # do we know the base?
                 self.ui.debug("found incomplete branch %s:%s\n"
                               % (short(n[0]), short(n[1])))
                 search.append(n) # schedule branch range for scanning
                 seenbranch[n] = 1
             else:
                 if n[2] in m and n[3] in m:
                     if n[1] not in fetch:
                         self.ui.debug("found new changeset %s\n" %
                                       short(n[1]))
                         fetch.append(n[1]) # earliest unknown
                         continue
 
                 r = []
                 for a in n[2:4]:
                     if a not in seen: r.append(a)
                     
                 if r:
                     self.ui.debug("requesting %s\n" %
                                 " ".join(map(short, r)))
                     for b in remote.branches(r):
                         self.ui.debug("received %s:%s\n" %
                                       (short(b[0]), short(b[1])))
                         if b[0] not in m and b[0] not in seen:
                             unknown.append(b)
   
         while search:
             n = search.pop(0)
             l = remote.between([(n[0], n[1])])[0]
             p = n[0]
             f = 1
             for i in l + [n[1]]:
                 if i in m:
                     if f <= 2:
                         self.ui.debug("found new branch changeset %s\n" %
                                           short(p))
                         fetch.append(p)
                     else:
                         self.ui.debug("narrowed branch search to %s:%s\n"
                                       % (short(p), short(i)))
                         search.append((p, i))
                     break
                 p, f = i, f * 2
 
         for f in fetch:
             if f in m:
                 raise "already have", short(f[:4])
 
         self.ui.note("adding new changesets starting at " +
                      " ".join([short(f) for f in fetch]) + "\n")
 
         return remote.changegroup(fetch)
     
     def changegroup(self, basenodes):
         nodes = self.newer(basenodes)
 
         # construct the link map
         linkmap = {}
         for n in nodes:
             linkmap[self.changelog.rev(n)] = n
 
         # construct a list of all changed files
         changed = {}
         for n in nodes:
             c = self.changelog.read(n)
             for f in c[3]:
                 changed[f] = 1
         changed = changed.keys()
         changed.sort()
 
         # the changegroup is changesets + manifests + all file revs
         revs = [ self.changelog.rev(n) for n in nodes ]
 
         for y in self.changelog.group(linkmap): yield y
         for y in self.manifest.group(linkmap): yield y
         for f in changed:
             yield struct.pack(">l", len(f) + 4) + f
             g = self.file(f).group(linkmap)
             for y in g:
                 yield y
 
     def addchangegroup(self, generator):
 
         class genread:
             def __init__(self, generator):
                 self.g = generator
                 self.buf = ""
             def read(self, l):
                 while l > len(self.buf):
                     try:
                         self.buf += self.g.next()
                     except StopIteration:
                         break
                 d, self.buf = self.buf[:l], self.buf[l:]
                 return d
                 
         def getchunk():
             d = source.read(4)
             if not d: return ""
             l = struct.unpack(">l", d)[0]
             if l <= 4: return ""
             return source.read(l - 4)
 
         def getgroup():
             while 1:
                 c = getchunk()
                 if not c: break
                 yield c
 
         def csmap(x):
             self.ui.debug("add changeset %s\n" % short(x))
             return self.changelog.count()
 
         def revmap(x):
             return self.changelog.rev(x)
 
         if not generator: return
         changesets = files = revisions = 0
 
         source = genread(generator)
         lock = self.lock()
         tr = self.transaction()
 
         # pull off the changeset group
         self.ui.status("adding changesets\n")
         co = self.changelog.tip()
         cn = self.changelog.addgroup(getgroup(), csmap, tr, 1) # unique
         changesets = self.changelog.rev(cn) - self.changelog.rev(co)
 
         # pull off the manifest group
         self.ui.status("adding manifests\n")
         mm = self.manifest.tip()
         mo = self.manifest.addgroup(getgroup(), revmap, tr)
 
         # process the files
         self.ui.status("adding file revisions\n")
         while 1:
             f = getchunk()
             if not f: break
             self.ui.debug("adding %s revisions\n" % f)
             fl = self.file(f)
             o = fl.tip()
             n = fl.addgroup(getgroup(), revmap, tr)
             revisions += fl.rev(n) - fl.rev(o)
             files += 1
 
         self.ui.status(("modified %d files, added %d changesets" +
                         " and %d new revisions\n")
                        % (files, changesets, revisions))
 
         tr.close()
         return
 
     def update(self, node, allow=False, force=False):
         pl = self.dirstate.parents()
         if not force and pl[1] != nullid:
             self.ui.warn("aborting: outstanding uncommitted merges\n")
             return
 
         p1, p2 = pl[0], node
         m1n = self.changelog.read(p1)[0]
         m2n = self.changelog.read(p2)[0]
         man = self.manifest.ancestor(m1n, m2n)
         m1 = self.manifest.read(m1n)
         mf1 = self.manifest.readflags(m1n)
         m2 = self.manifest.read(m2n)
         mf2 = self.manifest.readflags(m2n)
         ma = self.manifest.read(man)
         mfa = self.manifest.readflags(m2n)
 
         (c, a, d, u) = self.diffdir(self.root)
 
         # resolve the manifest to determine which files
         # we care about merging
         self.ui.note("resolving manifests\n")
         self.ui.debug(" ancestor %s local %s remote %s\n" %
                       (short(man), short(m1n), short(m2n)))
 
         merge = {}
         get = {}
         remove = []
 
         # construct a working dir manifest
         mw = m1.copy()
         mfw = mf1.copy()
         for f in a + c + u:
             mw[f] = ""
             mfw[f] = is_exec(self.wjoin(f))
         for f in d:
             if f in mw: del mw[f]
 
         for f, n in mw.iteritems():
             if f in m2:
                 s = 0
 
+                # are files different?
                 if n != m2[f]:
                     a = ma.get(f, nullid)
+                    # are both different from the ancestor?
                     if n != a and m2[f] != a:
                         self.ui.debug(" %s versions differ, resolve\n" % f)
                         merge[f] = (m1.get(f, nullid), m2[f])
                         # merge executable bits
                         # "if we changed or they changed, change in merge"
                         a, b, c = mfa.get(f, 0), mfw[f], mf2[f]
                         mode = ((a^b) | (a^c)) ^ a
                         merge[f] = (m1.get(f, nullid), m2[f], mode)
                         s = 1
-                    elif m2[f] != a:
+                    # is this an unmodified file or are we clobbering?
+                    elif mw[f] == m1[f] or force:
                         self.ui.debug(" remote %s is newer, get\n" % f)
                         get[f] = m2[f]
                         s = 1
 
                 if not s and mfw[f] != mf2[f]:
                     if force:
                         self.ui.debug(" updating permissions for %s\n" % f)
                         set_exec(self.wjoin(f), mf2[f])
                     else:
                         a, b, c = mfa.get(f, 0), mfw[f], mf2[f]
                         mode = ((a^b) | (a^c)) ^ a
                         if mode != b:
                             self.ui.debug(" updating permissions for %s\n" % f)
                             set_exec(self.wjoin(f), mode)
 
                 del m2[f]
             elif f in ma:
                 if not force and n != ma[f]:
                     r = self.ui.prompt(
                         (" local changed %s which remote deleted\n" % f) +
                         "(k)eep or (d)elete?", "[kd]", "k")
                     if r == "d":
                         remove.append(f)
                 else:
                     self.ui.debug("other deleted %s\n" % f)
                     remove.append(f) # other deleted it
             else:
                 if n == m1.get(f, nullid): # same as parent
                     self.ui.debug("remote deleted %s\n" % f)
                     remove.append(f)
                 else:
                     self.ui.debug("working dir created %s, keeping\n" % f)
 
         for f, n in m2.iteritems():
             if f[0] == "/": continue
             if not force and f in ma and n != ma[f]:
                 r = self.ui.prompt(
                     ("remote changed %s which local deleted\n" % f) +
                     "(k)eep or (d)elete?", "[kd]", "k")
                 if r == "d": remove.append(f)
             else:
                 self.ui.debug("remote created %s\n" % f)
                 get[f] = n
 
         del mw, m1, m2, ma
 
         if force:
             for f in merge:
                 get[f] = merge[f][1]
             merge = {}
 
         if not merge:
             # we don't need to do any magic, just jump to the new rev
             mode = 'n'
             p1, p2 = p2, nullid
         else:
             if not allow:
                 self.ui.status("the following files conflict:\n")
                 for f in merge:
                     self.ui.status(" %s\n" % f)
                 self.ui.warn("aborting update due to conflicting files!\n")
                 self.ui.status("(use update -m to allow a merge)\n")
                 return 1
             # we have to remember what files we needed to get/change
             # because any file that's different from either one of its
             # parents must be in the changeset
             mode = 'm'
 
         self.dirstate.setparents(p1, p2)
 
         # get the files we don't need to change
         files = get.keys()
         files.sort()
         for f in files:
             if f[0] == "/": continue
             self.ui.note("getting %s\n" % f)
             t = self.file(f).read(get[f])
             try:
                 self.wfile(f, "w").write(t)
             except IOError:
                 os.makedirs(os.path.dirname(wp))
                 self.wfile(f, "w").write(t)
             set_exec(self.wjoin(f), mf2[f])
             self.dirstate.update([f], mode)
 
         # merge the tricky bits
         files = merge.keys()
         files.sort()
         for f in files:
             self.ui.status("merging %s\n" % f)
             m, o, flag = merge[f]
             self.merge3(f, m, o)
             set_exec(wp, flag)
             self.dirstate.update([f], 'm')
 
         for f in remove:
             self.ui.note("removing %s\n" % f)
             os.unlink(f)
         if mode == 'n':
             self.dirstate.forget(remove)
         else:
             self.dirstate.update(remove, 'r')
 
     def merge3(self, fn, my, other):
         """perform a 3-way merge in the working directory"""
 
         def temp(prefix, node):
             pre = "%s~%s." % (os.path.basename(fn), prefix)
             (fd, name) = tempfile.mkstemp("", pre)
             f = os.fdopen(fd, "w")
             f.write(fl.revision(node))
             f.close()
             return name
 
         fl = self.file(fn)
         base = fl.ancestor(my, other)
         a = self.wjoin(fn)
         b = temp("other", other)
         c = temp("base", base)
 
         self.ui.note("resolving %s\n" % fn)
         self.ui.debug("file %s: other %s ancestor %s\n" %
                               (fn, short(other), short(base)))
 
         cmd = os.environ.get("HGMERGE", "hgmerge")
         r = os.system("%s %s %s %s" % (cmd, a, b, c))
         if r:
             self.ui.warn("merging %s failed!\n" % fn)
 
         os.unlink(b)
         os.unlink(c)
 
     def verify(self):
         filelinkrevs = {}
         filenodes = {}
         manifestchangeset = {}
         changesets = revisions = files = 0
         errors = 0
 
         self.ui.status("checking changesets\n")
         for i in range(self.changelog.count()):
             changesets += 1
             n = self.changelog.node(i)
             for p in self.changelog.parents(n):
                 if p not in self.changelog.nodemap:
                     self.ui.warn("changeset %s has unknown parent %s\n" %
                                  (short(n), short(p)))
                     errors += 1
             try:
                 changes = self.changelog.read(n)
             except Exception, inst:
                 self.ui.warn("unpacking changeset %s: %s\n" % (short(n), inst))
                 errors += 1
 
             manifestchangeset[changes[0]] = n
             for f in changes[3]:
                 filelinkrevs.setdefault(f, []).append(i)
 
         self.ui.status("checking manifests\n")
         for i in range(self.manifest.count()):
             n = self.manifest.node(i)
             for p in self.manifest.parents(n):
                 if p not in self.manifest.nodemap:
                     self.ui.warn("manifest %s has unknown parent %s\n" %
                             (short(n), short(p)))
                     errors += 1
             ca = self.changelog.node(self.manifest.linkrev(n))
             cc = manifestchangeset[n]
             if ca != cc:
                 self.ui.warn("manifest %s points to %s, not %s\n" %
                         (hex(n), hex(ca), hex(cc)))
                 errors += 1
 
             try:
                 delta = mdiff.patchtext(self.manifest.delta(n))
             except KeyboardInterrupt:
                 print "aborted"
                 sys.exit(0)
             except Exception, inst:
                 self.ui.warn("unpacking manifest %s: %s\n"
                              % (short(n), inst))
                 errors += 1
 
             ff = [ l.split('\0') for l in delta.splitlines() ]
             for f, fn in ff:
                 filenodes.setdefault(f, {})[bin(fn[:40])] = 1
 
         self.ui.status("crosschecking files in changesets and manifests\n")
         for f in filenodes:
             if f not in filelinkrevs:
                 self.ui.warn("file %s in manifest but not in changesets\n" % f)
                 errors += 1
 
         for f in filelinkrevs:
             if f not in filenodes:
                 self.ui.warn("file %s in changeset but not in manifest\n" % f)
                 errors += 1
 
         self.ui.status("checking files\n")
         ff = filenodes.keys()
         ff.sort()
         for f in ff:
             if f == "/dev/null": continue
             files += 1
             fl = self.file(f)
             nodes = { nullid: 1 }
             for i in range(fl.count()):
                 revisions += 1
                 n = fl.node(i)
 
                 if n not in filenodes[f]:
                     self.ui.warn("%s: %d:%s not in manifests\n"
                                  % (f, i, short(n)))
                     print len(filenodes[f].keys()), fl.count(), f
                     errors += 1
                 else:
                     del filenodes[f][n]
 
                 flr = fl.linkrev(n)
                 if flr not in filelinkrevs[f]:
                     self.ui.warn("%s:%s points to unexpected changeset %d\n"
                             % (f, short(n), fl.linkrev(n)))
                     errors += 1
                 else:
                     filelinkrevs[f].remove(flr)
 
                 # verify contents
                 try:
                     t = fl.read(n)
                 except Exception, inst:
                     self.ui.warn("unpacking file %s %s: %s\n"
                                  % (f, short(n), inst))
                     errors += 1
 
                 # verify parents
                 (p1, p2) = fl.parents(n)
                 if p1 not in nodes:
                     self.ui.warn("file %s:%s unknown parent 1 %s" %
                             (f, short(n), short(p1)))
                     errors += 1
                 if p2 not in nodes:
                     self.ui.warn("file %s:%s unknown parent 2 %s" %
                             (f, short(n), short(p1)))
                     errors += 1
                 nodes[n] = 1
 
             # cross-check
             for node in filenodes[f]:
                 self.ui.warn("node %s in manifests not in %s\n"
                              % (hex(n), f))
                 errors += 1
 
         self.ui.status("%d files, %d changesets, %d total revisions\n" %
                        (files, changesets, revisions))
 
         if errors:
             self.ui.warn("%d integrity errors encountered!\n" % errors)
             return 1
 
 class remoterepository:
     def __init__(self, ui, path):
         self.url = path
         self.ui = ui
 
     def do_cmd(self, cmd, **args):
         self.ui.debug("sending %s command\n" % cmd)
         q = {"cmd": cmd}
         q.update(args)
         qs = urllib.urlencode(q)
         cu = "%s?%s" % (self.url, qs)
         return urllib.urlopen(cu)
 
     def heads(self):
         d = self.do_cmd("heads").read()
         try:
             return map(bin, d[:-1].split(" "))
         except:
             self.ui.warn("unexpected response:\n" + d[:400] + "\n...\n")
             raise
 
     def branches(self, nodes):
         n = " ".join(map(hex, nodes))
         d = self.do_cmd("branches", nodes=n).read()
         try:
             br = [ tuple(map(bin, b.split(" "))) for b in d.splitlines() ]
             return br
         except:
             self.ui.warn("unexpected response:\n" + d[:400] + "\n...\n")
             raise
 
     def between(self, pairs):
         n = "\n".join(["-".join(map(hex, p)) for p in pairs])
         d = self.do_cmd("between", pairs=n).read()
         try:
             p = [ l and map(bin, l.split(" ")) or [] for l in d.splitlines() ]
             return p
         except:
             self.ui.warn("unexpected response:\n" + d[:400] + "\n...\n")
             raise
 
     def changegroup(self, nodes):
         n = " ".join(map(hex, nodes))
         zd = zlib.decompressobj()
         f = self.do_cmd("changegroup", roots=n)
         bytes = 0
         while 1:
             d = f.read(4096)
             bytes += len(d)
             if not d:
                 yield zd.flush()
                 break
             yield zd.decompress(d)
         self.ui.note("%d bytes of data transfered\n" % bytes)
 
 def repository(ui, path=None, create=0):
     if path and path[:7] == "http://":
         return remoterepository(ui, path)
     if path and path[:5] == "hg://":
         return remoterepository(ui, path.replace("hg://", "http://"))
     if path and path[:11] == "old-http://":
         return localrepository(ui, path.replace("old-http://", "http://"))
     else:
         return localrepository(ui, path, create)
 
 class httprangereader:
     def __init__(self, url):
         self.url = url
         self.pos = 0
     def seek(self, pos):
         self.pos = pos
     def read(self, bytes=None):
         opener = urllib2.build_opener(byterange.HTTPRangeHandler())
         urllib2.install_opener(opener)
         req = urllib2.Request(self.url)
         end = ''
         if bytes: end = self.pos + bytes
         req.add_header('Range', 'bytes=%d-%s' % (self.pos, end))
         f = urllib2.urlopen(req)
         return f.read()