rebase: empty revset should be a gentle no-op with exit code 1, not an error

hgext/rebase.py

@@ -228,15 +228,17 b' def rebase(ui, repo, **opts):'
             elif srcf:
                 src = scmutil.revrange(repo, [srcf])
                 if not src:
-                    raise util.Abort(_('empty "source" revision set - '
-                                       'nothing to rebase'))
+                    ui.status(_('empty "source" revision set - '
+                                'nothing to rebase\n'))
+                    return 1
                 rebaseset = repo.revs('(%ld)::', src)
                 assert rebaseset
             else:
                 base = scmutil.revrange(repo, [basef or '.'])
                 if not base:
-                    raise util.Abort(_('empty "base" revision set - '
-                                       "can't compute rebase set"))
+                    ui.status(_('empty "base" revision set - '
+                                "can't compute rebase set\n"))
+                    return 1
                 rebaseset = repo.revs(
                     '(children(ancestor(%ld, %d)) and ::(%ld))::',
                     base, dest, base)

tests/test-rebase-parameters.t

@@ -84,12 +84,12 b' These fail:'
   [1]
 
   $ hg rebase --source '1 & !1'
-  abort: empty "source" revision set - nothing to rebase
-  [255]
+  empty "source" revision set - nothing to rebase
+  [1]
 
   $ hg rebase --base '1 & !1'
-  abort: empty "base" revision set - can't compute rebase set
-  [255]
+  empty "base" revision set - can't compute rebase set
+  [1]
 
   $ hg rebase
   nothing to rebase - working directory parent is also destination