localrepo: drop "remote" argument from lookupbranch() (API)

localrepo: drop "remote" argument from lookupbranch() (API)

According to `hg grep --all lookupbranch`, the "remote" argument has
never been used ever since it was introduced in ca739acf1a98
(commands: add more robust support for 'hg log -b' (issue2078),
2010-04-12).

Differential Revision: https://phab.mercurial-scm.org/D3079

--- a/mercurial/localrepo.py	Sun Apr 01 22:48:32 2018 -0700
+++ b/mercurial/localrepo.py	Wed Apr 04 14:31:09 2018 -0700
@@ -1019,13 +1019,11 @@
     def lookup(self, key):
         return scmutil.revsymbol(self, key).node()
 
-    def lookupbranch(self, key, remote=None):
-        repo = remote or self
-        if key in repo.branchmap():
+    def lookupbranch(self, key):
+        if key in self.branchmap():
             return key
 
-        repo = (remote and remote.local()) and remote or self
-        return repo[key].branch()
+        return self[key].branch()
 
     def known(self, nodes):
         cl = self.changelog

--- a/mercurial/repository.py	Sun Apr 01 22:48:32 2018 -0700
+++ b/mercurial/repository.py	Wed Apr 04 14:31:09 2018 -0700
@@ -446,7 +446,7 @@
     def lookup(key):
         """Resolve the node for a revision."""
 
-    def lookupbranch(key, remote=None):
+    def lookupbranch(key):
         """Look up the branch name of the given revision or branch name."""
 
     def known(nodes):