document and fix findincoming

- add documentation about what the function does, notably
  the fact that it updates 'base'
- transform the workflow to a more simple 'if elif elif else'
- do not call remote.branches if not necessary
- some nodes where missing in 'base' (from what I understand,
  if the root of a branch is missing but one parent is present,
  the parent should be in 'base')
- add a testcase for an incorrect outgoing that is fixed by
  this cset
- add a testcase for an empty group bug, it needs fixing

tests/test-empty-group

@@ -0,0 +1,49 b''
+#!/bin/sh
+#
+#  A          B    
+#  
+#  3  4       3    
+#  |\/|       |\   
+#  |/\|       | \  
+#  1  2       1  2 
+#  \ /        \ /  
+#   0          0
+#
+# if the result of the merge of 1 and 2
+# is the same in 3 and 4, no new manifest
+# will be created and the manifest group
+# will be empty during the pull
+#
+# (plus we test a failure where outgoing
+# wrongly reported the number of csets)
+#
+
+hg init a
+cd a
+touch init
+hg ci -A -m 0 -d "1000000 0"
+touch x y
+hg ci -A -m 1 -d "1000000 0"
+hg update 0
+touch x y
+hg ci -A -m 2 -d "1000000 0"
+hg merge 1
+hg ci -A -m m1 -d "1000000 0"
+#hg log
+#hg debugindex .hg/00manifest.i
+hg update -C 1
+hg merge 2
+hg ci -A -m m2 -d "1000000 0"
+#hg log
+#hg debugindex .hg/00manifest.i
+
+cd ..
+hg clone -r 3 a b
+hg clone -r 4 a c
+hg -R a outgoing b
+hg -R a outgoing c
+hg -R b outgoing c
+hg -R c outgoing b
+
+hg -R b pull a
+hg -R c pull a

tests/test-empty-group.out

@@ -0,0 +1,72 b''
+adding init
+adding x
+adding y
+0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+adding x
+adding y
+0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+(branch merge, don't forget to commit)
+0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+(branch merge, don't forget to commit)
+requesting all changes
+adding changesets
+adding manifests
+adding file changes
+added 4 changesets with 3 changes to 3 files
+3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+requesting all changes
+adding changesets
+adding manifests
+adding file changes
+added 4 changesets with 3 changes to 3 files
+3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+searching for changes
+changeset:   4:fdb3c546e859
+tag:         tip
+parent:      1:1f703b3fcbc6
+parent:      2:de997049e034
+user:        test
+date:        Mon Jan 12 13:46:40 1970 +0000
+summary:     m2
+
+searching for changes
+changeset:   3:f40f830c0024
+parent:      2:de997049e034
+parent:      1:1f703b3fcbc6
+user:        test
+date:        Mon Jan 12 13:46:40 1970 +0000
+summary:     m1
+
+searching for changes
+changeset:   3:f40f830c0024
+tag:         tip
+parent:      2:de997049e034
+parent:      1:1f703b3fcbc6
+user:        test
+date:        Mon Jan 12 13:46:40 1970 +0000
+summary:     m1
+
+searching for changes
+changeset:   3:fdb3c546e859
+tag:         tip
+parent:      1:1f703b3fcbc6
+parent:      2:de997049e034
+user:        test
+date:        Mon Jan 12 13:46:40 1970 +0000
+summary:     m2
+
+pulling from a
+searching for changes
+adding changesets
+adding manifests
+adding file changes
+added 1 changesets with 0 changes to 0 files (+1 heads)
+(run 'hg heads' to see heads, 'hg merge' to merge)
+pulling from a
+searching for changes
+adding changesets
+adding manifests
+adding file changes
+added 1 changesets with 0 changes to 0 files (+1 heads)
+(run 'hg heads' to see heads, 'hg merge' to merge)

mercurial/localrepo.py

@@ -899,6 +899,21 b' class localrepository(object):'
         return r
 
     def findincoming(self, remote, base=None, heads=None, force=False):
+        """Return list of roots of the subsets of missing nodes from remote
+
+        If base dict is specified, assume that these nodes and their parents
+        exist on the remote side and that no child of a node of base exists
+        in both remote and self.
+        Furthermore base will be updated to include the nodes that exists
+        in self and remote but no children exists in self and remote.
+        If a list of heads is specified, return only nodes which are heads
+        or ancestors of these heads.
+
+        All the ancestors of base are in self and in remote.
+        All the descendants of the list returned are missing in self.
+        (and so we know that the rest of the nodes are missing in remote, see
+        outgoing)
+        """
         m = self.changelog.nodemap
         search = []
         fetch = {}
@@ -911,6 +926,7 b' class localrepository(object):'
             heads = remote.heads()
 
         if self.changelog.tip() == nullid:
+            base[nullid] = 1
             if heads != [nullid]:
                 return [nullid]
             return []
@@ -929,7 +945,7 b' class localrepository(object):'
         if not unknown:
             return []
 
-        rep = {}
+        req = dict.fromkeys(unknown)
         reqcnt = 0
 
         # search through remote branches
@@ -946,12 +962,12 b' class localrepository(object):'
 
                 self.ui.debug(_("examining %s:%s\n")
                               % (short(n[0]), short(n[1])))
-                if n[0] == nullid:
-                    break
-                if n in seenbranch:
+                if n[0] == nullid: # found the end of the branch
+                    pass
+                elif n in seenbranch:
                     self.ui.debug(_("branch already found\n"))
                     continue
-                if n[1] and n[1] in m: # do we know the base?
+                elif 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
@@ -962,14 +978,14 b' class localrepository(object):'
                             self.ui.debug(_("found new changeset %s\n") %
                                           short(n[1]))
                             fetch[n[1]] = 1 # earliest unknown
-                            base[n[2]] = 1 # latest known
-                            continue
+                        for p in n[2:4]:
+                            if p in m:
+                                base[p] = 1 # latest known
 
-                    for a in n[2:4]:
-                        if a not in rep:
-                            r.append(a)
-                            rep[a] = 1
-
+                    for p in n[2:4]:
+                        if p not in req and p not in m:
+                            r.append(p)
+                            req[p] = 1
                 seen[n[0]] = 1
 
             if r:
@@ -980,12 +996,7 b' class localrepository(object):'
                     for b in remote.branches(r[p:p+10]):
                         self.ui.debug(_("received %s:%s\n") %
                                       (short(b[0]), short(b[1])))
-                        if b[0] in m:
-                            self.ui.debug(_("found base node %s\n")
-                                          % short(b[0]))
-                            base[b[0]] = 1
-                        elif b[0] not in seen:
-                            unknown.append(b)
+                        unknown.append(b)
 
         # do binary search on the branches we found
         while search: