[PATCH STABLE] rebase: fix rebase with no common ancestors (issue4446)

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1415645082 28800
#      Mon Nov 10 10:44:42 2014 -0800
# Node ID 15e6fe3cd01beba4232780cdef715d47cc0b0df5
# Parent  2d54aa5397cdb1c697673ba10b7618d5ac25c69e
rebase: fix rebase with no common ancestors (issue4446)

The new rebase revset didn't check for the case when there are no common
ancestors. Now it does. The new behavior should be the same as the pre-3.2
behavior. Added a test.

diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -274,8 +274,12 @@ def rebase(ui, repo, **opts):
                                 "can't compute rebase set\n"))
                     return 1
                 commonanc = repo.revs('ancestor(%ld, %d)', base, dest).first()
-                rebaseset = repo.revs('(%d::(%ld) - %d)::',
-                                      commonanc, base, commonanc)
+                if commonanc is not None:
+                    rebaseset = repo.revs('(%d::(%ld) - %d)::',
+                                          commonanc, base, commonanc)
+                else:
+                    rebaseset = []
+
                 if not rebaseset:
                     # transform to list because smartsets are not comparable to
                     # lists. This should be improved to honor laziness of
diff --git a/tests/test-rebase-parameters.t b/tests/test-rebase-parameters.t
--- a/tests/test-rebase-parameters.t
+++ b/tests/test-rebase-parameters.t
@@ -468,3 +468,17 @@ Test --tool parameter:
   [255]
 
   $ cd ..
+
+No common ancestor
+
+  $ hg init separaterepo
+  $ cd separaterepo
+  $ touch a
+  $ hg commit -Aqm a
+  $ hg up -q null
+  $ touch b
+  $ hg commit -Aqm b
+  $ hg rebase -d 0
+  nothing to rebase from d7486e00c6f1 to 3903775176ed
+  [1]
+  $ cd ..