149 

   150 update to older changeset and then refuse rollback, because

   151 that would lose data (issue2998)

   152   $ cd ../t

   153   $ hg -q update

   154   $ rm `hg status -un`

   155   $ template='{rev}:{node|short}  [{branch}]  {desc|firstline}\n'

   156   $ echo 'valuable new file' > b

   157   $ echo 'valuable modification' >> a

   158   $ hg commit -A -m'a valuable change'

   159   adding b

   160   $ hg update 0

   161   1 files updated, 0 files merged, 1 files removed, 0 files unresolved

   162   $ hg rollback

   163   abort: rollback of last commit while not checked out may lose data (use -f to force)

   164   [255]

   165   $ hg tip -q

   166   2:4d9cd3795eea

   167   $ hg rollback -f

   168   repository tip rolled back to revision 1 (undo commit)

   169   $ hg status

   170   $ hg log --removed b   # yep, it's gone

   171 

   172 same again, but emulate an old client that doesn't write undo.desc

   173   $ hg -q update

   174   $ echo 'valuable modification redux' >> a

   175   $ hg commit -m'a valuable change redux'

   176   $ rm .hg/undo.desc

   177   $ hg update 0

   178   1 files updated, 0 files merged, 0 files removed, 0 files unresolved

   179   $ hg rollback

   180   rolling back unknown transaction

   181   $ cat a

   182   a