localrepo: add branchtip() method for faster single-branch lookups

For the PyPy repo with 744 branches and 843 branch heads, this brings
hg log -r default over NFS from:

   CallCount    Recursive    Total(ms)   Inline(ms) module:lineno(function)
        3249            0      1.3222      1.3222   <open>
        3244            0      0.6211      0.6211   <method 'close' of 'file' objects>
        3243            0      0.0800      0.0800   <method 'read' of 'file' objects>
        3241            0      0.0660      0.0660   <method 'seek' of 'file' objects>
        3905            0      0.0476      0.0476   <zlib.decompress>
        3281            0      2.6756      0.0472   mercurial.changelog:182(read)
       +3281            0      2.5256      0.0453   +mercurial.revlog:881(revision)
       +3276            0      0.0389      0.0196   +mercurial.changelog:28(decodeextra)
       +6562            0      0.0123      0.0123   +<method 'split' of 'str' objects>
       +6562            0      0.0408      0.0073   +mercurial.encoding:61(tolocal)
       +3281            0      0.0054      0.0054   +<method 'index' of 'str' objects>
        3241            0      2.2464      0.0456   mercurial.revlog:818(_loadchunk)
       +3241            0      0.6205      0.6205   +<method 'close' of 'file' objects>
       +3241            0      0.0765      0.0765   +<method 'read' of 'file' objects>
       +3241            0      0.0660      0.0660   +<method 'seek' of 'file' objects>
       +3241            0      1.4209      0.0135   +mercurial.store:374(__call__)
       +3241            0      0.0122      0.0107   +mercurial.revlog:810(_addchunk)
        3281            0      2.5256      0.0453   mercurial.revlog:881(revision)
       +3280            0      0.0175      0.0175   +mercurial.revlog:305(rev)
       +3281            0      2.2819      0.0119   +mercurial.revlog:847(_chunkraw)
       +3281            0      0.0603      0.0083   +mercurial.revlog:945(_checkhash)
       +3281            0      0.0051      0.0051   +mercurial.revlog:349(flags)
       +3281            0      0.0040      0.0040   +<mercurial.mpatch.patches>
       13682            0      0.0479      0.0248   <method 'decode' of 'str' objects>
       +7418            0      0.0228      0.0076   +encodings.utf_8:15(decode)
          +1            0      0.0003      0.0000   +encodings:71(search_function)
        3248            0      1.3995      0.0246   mercurial.scmutil:218(__call__)
       +3248            0      1.3222      1.3222   +<open>
       +3248            0      0.0235      0.0184   +os.path:80(split)
       +3248            0      0.0084      0.0068   +mercurial.scmutil:92(__call__)
Time: real 2.750 secs (user 0.680+0.000 sys 0.360+0.000)

down to:

   CallCount    Recursive    Total(ms)   Inline(ms) module:lineno(function)
          55           31      0.0197      0.0163   <__import__>
          +1            0      0.0006      0.0002   +mercurial.context:8(<module>)
          +1            0      0.0042      0.0001   +mercurial.revlog:12(<module>)
          +1            0      0.0002      0.0001   +mercurial.match:8(<module>)
          +1            0      0.0003      0.0001   +mercurial.dirstate:7(<module>)
          +1            0      0.0057      0.0001   +mercurial.changelog:8(<module>)
           1            0      0.0117      0.0032   mercurial.localrepo:525(_readbranchcache)
        +844            0      0.0015      0.0015   +<binascii.unhexlify>
        +845            0      0.0010      0.0010   +<method 'split' of 'str' objects>
        +843            0      0.0045      0.0009   +mercurial.encoding:61(tolocal)
        +843            0      0.0004      0.0004   +<method 'setdefault' of 'dict' objects>
          +1            0      0.0003      0.0003   +<method 'close' of 'file' objects>
           3            0      0.0029      0.0029   <method 'read' of 'file' objects>
           9            0      0.0018      0.0018   <open>
         990            0      0.0017      0.0017   <binascii.unhexlify>
          53            0      0.0016      0.0016   mercurial.demandimport:43(__init__)
         862            0      0.0015      0.0015   <_codecs.utf_8_decode>
         862            0      0.0037      0.0014   <method 'decode' of 'str' objects>
        +862            0      0.0023      0.0008   +encodings.utf_8:15(decode)
         981            0      0.0011      0.0011   <method 'split' of 'str' objects>
         861            0      0.0046      0.0009   mercurial.encoding:61(tolocal)
        +861            0      0.0037      0.0014   +<method 'decode' of 'str' objects>
         862            0      0.0023      0.0008   encodings.utf_8:15(decode)
        +862            0      0.0015      0.0015   +<_codecs.utf_8_decode>
           4            0      0.0008      0.0008   <method 'close' of 'file' objects>
         179          154      0.0202      0.0004   mercurial.demandimport:83(__getattribute__)
         +36           11      0.0199      0.0003   +mercurial.demandimport:55(_load)
         +72            0      0.0001      0.0001   +mercurial.demandimport:83(__getattribute__)
         +36            0      0.0000      0.0000   +<getattr>
           1            0      0.0015      0.0004   mercurial.tags:148(_readtagcache)
Time: real 0.060 secs (user 0.030+0.000 sys 0.010+0.000)

hgext/fetch.py

@@ -38,7 +38,10 b" def fetch(ui, repo, source='default', **"
 
     parent, p2 = repo.dirstate.parents()
     branch = repo.dirstate.branch()
-    branchnode = repo.branchtags().get(branch)
+    try:
+        branchnode = repo.branchtip(branch)
+    except error.RepoLookupError:
+        branchnode = None
     if parent != branchnode:
         raise util.Abort(_('working dir not at branch tip '
                            '(use "hg update" to check out branch tip)'))

mercurial/bookmarks.py

@@ -7,7 +7,7 b''
 
 from mercurial.i18n import _
 from mercurial.node import hex
-from mercurial import encoding, util
+from mercurial import encoding, error, util
 import errno, os
 
 def valid(mark):
@@ -140,8 +140,8 b' def unsetcurrent(repo):'
 
 def updatecurrentbookmark(repo, oldnode, curbranch):
     try:
-        return update(repo, oldnode, repo.branchtags()[curbranch])
-    except KeyError:
+        return update(repo, oldnode, repo.branchtip(curbranch))
+    except error.RepoLookupError:
         if curbranch == "default": # no default branch!
             return update(repo, oldnode, repo.lookup("tip"))
         else:

mercurial/commands.py

@@ -827,7 +827,7 b' def bookmark(ui, repo, mark=None, rev=No'
         if mark in marks and not force:
             raise util.Abort(_("bookmark '%s' already exists "
                                "(use -f to force)") % mark)
-        if ((mark in repo.branchtags() or mark == repo.dirstate.branch())
+        if ((mark in repo.branchmap() or mark == repo.dirstate.branch())
             and not force):
             raise util.Abort(
                 _("a bookmark cannot have the name of an existing branch"))
@@ -903,7 +903,7 b' def branch(ui, repo, label=None, **opts)'
             repo.dirstate.setbranch(label)
             ui.status(_('reset working directory to branch %s\n') % label)
         elif label:
-            if not opts.get('force') and label in repo.branchtags():
+            if not opts.get('force') and label in repo.branchmap():
                 if label not in [p.branch() for p in repo.parents()]:
                     raise util.Abort(_('a branch of the same name already'
                                        ' exists'),

mercurial/context.py

@@ -78,10 +78,12 b' class changectx(object):'
             self._node = repo._tagscache.tags[changeid]
             self._rev = repo.changelog.rev(self._node)
             return
-        if changeid in repo.branchtags():
-            self._node = repo.branchtags()[changeid]
+        try:
+            self._node = repo.branchtip(changeid)
             self._rev = repo.changelog.rev(self._node)
             return
+        except error.RepoLookupError:
+            pass
 
         self._node = repo.changelog._partialmatch(changeid)
         if self._node is not None:

mercurial/hgweb/webcommands.py

@@ -794,7 +794,11 b' def graph(web, req, tmpl):'
         desc = cgi.escape(templatefilters.nonempty(desc))
         user = cgi.escape(templatefilters.person(ctx.user()))
         branch = ctx.branch()
-        branch = branch, web.repo.branchtags().get(branch) == ctx.node()
+        try:
+            branchnode = web.repo.branchtip(branch)
+        except error.RepoLookupError:
+            branchnode = None
+        branch = branch, branchnode == ctx.node()
         data.append((node, vtx, edges, desc, user, age, branch, ctx.tags(),
                      ctx.bookmarks()))
 

mercurial/hgweb/webutil.py

@@ -98,16 +98,23 b' def nodebranchdict(repo, ctx):'
     branches = []
     branch = ctx.branch()
     # If this is an empty repo, ctx.node() == nullid,
-    # ctx.branch() == 'default', but branchtags() is
-    # an empty dict. Using dict.get avoids a traceback.
-    if repo.branchtags().get(branch) == ctx.node():
+    # ctx.branch() == 'default'.
+    try:
+        branchnode = repo.branchtip(branch)
+    except error.RepoLookupError:
+        branchnode = None
+    if branchnode == ctx.node():
         branches.append({"name": branch})
     return branches
 
 def nodeinbranch(repo, ctx):
     branches = []
     branch = ctx.branch()
-    if branch != 'default' and repo.branchtags().get(branch) != ctx.node():
+    try:
+        branchnode = repo.branchtip(branch)
+    except error.RepoLookupError:
+        branchnode = None
+    if branch != 'default' and branchnode != ctx.node():
         branches.append({"name": branch})
     return branches
 

mercurial/localrepo.py

@@ -507,17 +507,27 b' class localrepository(repo.repository):'
         self.updatebranchcache()
         return self._branchcache
 
+    def _branchtip(self, heads):
+        '''return the tipmost branch head in heads'''
+        tip = heads[-1]
+        for h in reversed(heads):
+            if 'close' not in self.changelog.read(h)[5]:
+                tip = h
+                break
+        return tip
+
+    def branchtip(self, branch):
+        '''return the tip node for a given branch'''
+        if branch not in self.branchmap():
+            raise error.RepoLookupError(_("unknown branch '%s'") % branch)
+        return self._branchtip(self.branchmap()[branch])
+
     def branchtags(self):
         '''return a dict where branch names map to the tipmost head of
         the branch, open heads come before closed'''
         bt = {}
         for bn, heads in self.branchmap().iteritems():
-            tip = heads[-1]
-            for h in reversed(heads):
-                if 'close' not in self.changelog.read(h)[5]:
-                    tip = h
-                    break
-            bt[bn] = tip
+            bt[bn] = self._branchtip(heads)
         return bt
 
     def _readbranchcache(self):

mercurial/merge.py

@@ -7,7 +7,7 b''
 
 from node import nullid, nullrev, hex, bin
 from i18n import _
-import scmutil, util, filemerge, copies, subrepo
+import error, scmutil, util, filemerge, copies, subrepo
 import errno, os, shutil
 
 class mergestate(object):
@@ -529,8 +529,8 b' def update(repo, node, branchmerge, forc'
         if node is None:
             # tip of current branch
             try:
-                node = repo.branchtags()[wc.branch()]
-            except KeyError:
+                node = repo.branchtip(wc.branch())
+            except error.RepoLookupError:
                 if wc.branch() == "default": # no default branch!
                     node = repo.lookup("tip") # update to tip
                 else: