rebase: make sure the newancestor is used during the whole update

(issue1561)

Before this change, newancestor was used only once as a replacement
for ancestor.ancestor, but merge.update calls ancestor.ancestor
several times, so it ends up with the "wrong" ancestor (the real
ancestor, but we want the parent of the rebased changeset for all but
the first rebased changeset).

Added a new test case for this: test-rebase-newancestor.

Also, in one scenario in test-rebase-collapse, there was a spurious
conflict caused by the same issue, so that test case was fixed by
removing the now unneeded conflict resolution and the output was
adapted accordingly.

tests/test-rebase-newancestor

@@ -0,0 +1,31 b''
+#!/bin/sh
+
+echo "[extensions]" >> $HGRCPATH
+echo "graphlog=" >> $HGRCPATH
+echo "rebase=" >> $HGRCPATH
+
+rm -rf repo
+hg init repo
+cd repo
+
+echo A > a
+echo >> a
+hg commit -AmA -u test -d '0 0'
+
+echo B > a
+echo >> a
+hg commit -mB -u test -d '1 0'
+
+echo C > a
+echo >> a
+hg commit -mC -u test -d '2 0'
+
+hg up -C 0
+echo D >> a
+hg commit -AmAD -u test -d '3 0'
+
+hg glog --template '{rev}:{desc} {node|short}\n'
+hg rebase -q -s 1 -d 3 2>&1 | grep -v 'saving bundle'
+hg glog --template '{rev}:{desc} {node|short}\n'
+
+exit 0

tests/test-rebase-newancestor.out

@@ -0,0 +1,19 b''
+adding a
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+created new head
+@  3:AD 1d4e82ed3c2a
+|
+| o  2:C 7e1afe9214b2
+| |
+| o  1:B 0a6620c3c26a
+|/
+o  0:A 1e635d440a73
+
+@  3:C 0c5887756284
+|
+o  2:B 4f208f4a1507
+|
+o  1:AD 1d4e82ed3c2a
+|
+o  0:A 1e635d440a73
+

hgext/rebase.py

@@ -27,17 +27,19 b' def rebasemerge(repo, rev, first=False):'
     oldancestor = ancestor.ancestor
 
     def newancestor(a, b, pfunc):
-        ancestor.ancestor = oldancestor
         if b == rev:
             return repo[rev].parents()[0].rev()
-        return ancestor.ancestor(a, b, pfunc)
+        return oldancestor(a, b, pfunc)
 
     if not first:
         ancestor.ancestor = newancestor
     else:
         repo.ui.debug("first revision, do not change ancestor\n")
-    stats = merge.update(repo, rev, True, True, False)
-    return stats
+    try:
+        stats = merge.update(repo, rev, True, True, False)
+        return stats
+    finally:
+        ancestor.ancestor = oldancestor
 
 def rebase(ui, repo, **opts):
     """move changeset (and descendants) to a different branch

tests/test-rebase-collapse

@@ -130,12 +130,7 b" hg glog --template '{rev}: {desc}\\n'"
 
 echo
 echo '% Rebase and collapse - E onto I'
-hg rebase -s 4 --collapse 
-
-echo '% Fix conflict and continue'
-echo 'Resolved merge' > E
-hg resolve -m E
-hg rebase -c 2>&1 | sed 's/\(saving bundle to \).*/\1/'
+hg rebase -s 4 --collapse 2>&1 | sed 's/\(saving bundle to \).*/\1/'
 
 hg glog  --template '{rev}: {desc}\n'
 

tests/test-rebase-collapse.out

@@ -145,10 +145,6 b' o 0: A'
 
 % Rebase and collapse - E onto I
 merging E
-warning: conflicts during merge.
-merging E failed!
-abort: fix unresolved conflicts with hg resolve then run hg rebase --continue
-% Fix conflict and continue
 saving bundle to 
 adding branch
 adding changesets
@@ -179,7 +175,7 b' E'
 G
 I
 Cat E:
-Resolved merge
+F
 
 @  5: F
 |