Merge branch 'jc/rebase-limit'

* jc/rebase-limit:
  rebase: allow rebasing onto different base.

diff --cc git-rebase.sh
index f84160d,a2651be..21c3d83
--- 1/git-rebase.sh
--- 2/git-rebase.sh
+++ b/git-rebase.sh
@@@ -30,21 -68,11 +68,20 @@@ case "$diff" i
        ;;
  esac
  
- # The other head is given.  Make sure it is valid.
- other=$(git-rev-parse --verify "$1^0") || usage
- 
- # Make sure the branch to rebase is valid.
- head=$(git-rev-parse --verify "${2-HEAD}^0") || exit
+ # The upstream head must be given.  Make sure it is valid.
+ upstream_name="$1"
+ upstream=`git rev-parse --verify "${upstream_name}^0"` ||
+     die "invalid upsteram $upstream_name"
  
 +# If a hook exists, give it a chance to interrupt
 +if test -x "$GIT_DIR/hooks/pre-rebase"
 +then
 +      "$GIT_DIR/hooks/pre-rebase" ${1+"$@"} || {
 +              echo >&2 "The pre-rebase hook refused to rebase."
 +              exit 1
 +      }
 +fi
 +
  # If the branch to rebase is given, first switch to it.
  case "$#" in
  2)