onto=              rebase onto given branch instead of upstream
 p,preserve-merges  try to recreate merges instead of ignoring them
 s,strategy=        use the given merge strategy
+no-ff              cherry-pick all commits, even if unchanged
 m,merge            always used (no-op)
 i,interactive      always used (no-op)
  Actions:
 # command is processed, this file is deleted.
 AMEND="$DOTEST"/amend
 
+# For the post-rewrite hook, we make a list of rewritten commits and
+# their new sha1s.  The rewritten-pending list keeps the sha1s of
+# commits that have been processed, but not committed yet,
+# e.g. because they are waiting for a 'squash' command.
+REWRITTEN_LIST="$DOTEST"/rewritten-list
+REWRITTEN_PENDING="$DOTEST"/rewritten-pending
+
 PRESERVE_MERGES=
 STRATEGY=
 ONTO=
 OK_TO_SKIP_PRE_REBASE=
 REBASE_ROOT=
 AUTOSQUASH=
+NEVER_FF=
 
 GIT_CHERRY_PICK_HELP="  After resolving the conflicts,
 mark the corrected paths with 'git add <paths>', and
 }
 
 die_with_patch () {
+       echo "$1" > "$DOTEST"/stopped-sha
        make_patch "$1"
        git rerere
        die "$2"
 }
 
 pick_one () {
-       no_ff=
-       case "$1" in -n) sha1=$2; no_ff=t ;; *) sha1=$1 ;; esac
+       ff=--ff
+       case "$1" in -n) sha1=$2; ff= ;; *) sha1=$1 ;; esac
+       case "$NEVER_FF" in '') ;; ?*) ff= ;; esac
        output git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
        test -d "$REWRITTEN" &&
                pick_one_preserving_merges "$@" && return
                output git cherry-pick "$@"
                return
        fi
-       parent_sha1=$(git rev-parse --verify $sha1^) ||
-               die "Could not get the parent of $sha1"
-       current_sha1=$(git rev-parse --verify HEAD)
-       if test -z "$no_ff" && test "$current_sha1" = "$parent_sha1"
-       then
-               output git reset --hard $sha1
-               output warn Fast-forward to $(git rev-parse --short $sha1)
-       else
-               output git cherry-pick "$@"
-       fi
+       output git cherry-pick $ff "$@"
 }
 
 pick_one_preserving_merges () {
                                printf "%s\n" "$msg" > "$GIT_DIR"/MERGE_MSG
                                die_with_patch $sha1 "Error redoing merge $sha1"
                        fi
+                       echo "$sha1 $(git rev-parse HEAD^0)" >> "$REWRITTEN_LIST"
                        ;;
                *)
                        output git cherry-pick "$@" ||
        die_with_patch $1 ""
 }
 
+flush_rewritten_pending() {
+       test -s "$REWRITTEN_PENDING" || return
+       newsha1="$(git rev-parse HEAD^0)"
+       sed "s/$/ $newsha1/" < "$REWRITTEN_PENDING" >> "$REWRITTEN_LIST"
+       rm -f "$REWRITTEN_PENDING"
+}
+
+record_in_rewritten() {
+       oldsha1="$(git rev-parse $1)"
+       echo "$oldsha1" >> "$REWRITTEN_PENDING"
+
+       case "$(peek_next_command)" in
+           squash|s|fixup|f)
+               ;;
+           *)
+               flush_rewritten_pending
+               ;;
+       esac
+}
+
 do_next () {
        rm -f "$MSG" "$AUTHOR_SCRIPT" "$AMEND" || exit
        read command sha1 rest < "$TODO"
                mark_action_done
                pick_one $sha1 ||
                        die_with_patch $sha1 "Could not apply $sha1... $rest"
+               record_in_rewritten $sha1
                ;;
        reword|r)
                comment_for_reflog reword
                mark_action_done
                pick_one $sha1 ||
                        die_with_patch $sha1 "Could not apply $sha1... $rest"
-               git commit --amend
+               git commit --amend --no-post-rewrite
+               record_in_rewritten $sha1
                ;;
        edit|e)
                comment_for_reflog edit
                mark_action_done
                pick_one $sha1 ||
                        die_with_patch $sha1 "Could not apply $sha1... $rest"
+               echo "$sha1" > "$DOTEST"/stopped-sha
                make_patch $sha1
                git rev-parse --verify HEAD > "$AMEND"
                warn "Stopped at $sha1... $rest"
                        rm -f "$SQUASH_MSG" "$FIXUP_MSG"
                        ;;
                esac
+               record_in_rewritten $sha1
                ;;
        *)
                warn "Unknown command: $command $sha1 $rest"
                test ! -f "$DOTEST"/verbose ||
                        git diff-tree --stat $(cat "$DOTEST"/head)..HEAD
        } &&
+       {
+               test -s "$REWRITTEN_LIST" &&
+               git notes copy --for-rewrite=rebase < "$REWRITTEN_LIST" ||
+               true # we don't care if this copying failed
+       } &&
+       if test -x "$GIT_DIR"/hooks/post-rewrite &&
+               test -s "$REWRITTEN_LIST"; then
+               "$GIT_DIR"/hooks/post-rewrite rebase < "$REWRITTEN_LIST"
+               true # we don't care if this hook failed
+       fi &&
        rm -rf "$DOTEST" &&
        git gc --auto &&
        warn "Successfully rebased and updated $HEADNAME."
                esac
                echo "$command${sha1:+ }$sha1${rest:+ }$rest" >&$fd
        done <"$TODO" >"$TODO.new" 3>>"$DONE" &&
-       mv -f "$TODO".new "$TODO" ||
+       mv -f "$TODO".new "$TODO" &&
+       case "$(peek_next_command)" in
+       squash|s|fixup|f)
+               record_in_rewritten "$ONTO"
+               ;;
+       esac ||
        die "Could not skip unnecessary pick commands"
 }
 
                        }
                fi
 
+               record_in_rewritten "$(cat "$DOTEST"/stopped-sha)"
+
                require_clean_work_tree
                do_rest
                ;;
        -i)
                # yeah, we know
                ;;
+       --no-ff)
+               NEVER_FF=t
+               ;;
        --root)
                REBASE_ROOT=t
                ;;
 
                if test ! -z "$1"
                then
-                       output git show-ref --verify --quiet "refs/heads/$1" ||
-                               die "Invalid branchname: $1"
                        output git checkout "$1" ||
                                die "Could not checkout $1"
                fi
                has_action "$TODO" ||
                        die_abort "Nothing to do"
 
-               test -d "$REWRITTEN" || skip_unnecessary_picks
+               test -d "$REWRITTEN" || test -n "$NEVER_FF" || skip_unnecessary_picks
 
+               output git checkout $ONTO || die_abort "could not detach HEAD"
                git update-ref ORIG_HEAD $HEAD
-               output git checkout $ONTO && do_rest
+               do_rest
                ;;
        esac
        shift