diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -52,6 +52,7 @@ testpats = [
     (r'/bin/', "don't use explicit paths for tools"),
     (r'\$PWD', "don't use $PWD, use `pwd`"),
     (r'[^\n]\Z', "no trailing newline"),
+    (r'export.*=', "don't export and assign at once"),
 ]
 
 testfilters = [
diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -38,17 +38,16 @@ def rebase(ui, repo, **opts):
     rebasing, but new changesets are added as its descendants.)
 
     You can specify which changesets to rebase in two ways: as a
-    \"source\" changeset or as a \"base\" changeset. Both are
-    shorthand for a topologically related set of changesets (the
-    \"source branch\"). If you specify source (``-s/--source``),
-    rebase will rebase that changeset and all of its descendants onto
-    dest. If you specify base (``-b/--base``), rebase will select
-    ancestors of base back to but not including the common ancestor
-    with dest. Thus, ``-b`` is less precise but more convenient than
-    ``-s``: you can specify any changeset in the source branch, and
-    rebase will select the whole branch. If you specify neither ``-s``
-    nor ``-b``, rebase uses the parent of the working directory as the
-    base.
+    "source" changeset or as a "base" changeset. Both are shorthand
+    for a topologically related set of changesets (the "source
+    branch"). If you specify source (``-s/--source``), rebase will
+    rebase that changeset and all of its descendants onto dest. If you
+    specify base (``-b/--base``), rebase will select ancestors of base
+    back to but not including the common ancestor with dest. Thus,
+    ``-b`` is less precise but more convenient than ``-s``: you can
+    specify any changeset in the source branch, and rebase will select
+    the whole branch. If you specify neither ``-s`` nor ``-b``, rebase
+    uses the parent of the working directory as the base.
 
     By default, rebase recreates the changesets in the source branch
     as descendants of dest and then destroys the originals. Use
diff --git a/tests/test-merge-default b/tests/test-merge-default
--- a/tests/test-merge-default
+++ b/tests/test-merge-default
@@ -24,7 +24,7 @@ hg merge
 
 hg up
 echo % should fail because \> 2 heads
-export HGMERGE=internal:other
+HGMERGE=internal:other; export HGMERGE
 hg merge
 
 echo % should succeed