zsh completion: add `forget` and `rollback` commands

contrib/zsh_completion

@@ -566,6 +566,11 b' typeset -A _hg_cmd_globals'
   '*:revision:_hg_labels'
 }
 
+_hg_cmd_forget() {
+  _arguments -s -w : $_hg_global_opts \
+  '*:file:_hg_files'
+}
+
 _hg_cmd_graft() {
   _arguments -s -w : $_hg_global_opts \
   '(--continue -c)'{-c,--continue}'[resume interrupted graft]' \
@@ -777,6 +782,11 b' typeset -A _hg_cmd_globals'
   fi
 }
 
+_hg_cmd_rollback() {
+  _arguments -s -w : $_hg_global_opts $_hg_dryrun_opts \
+  '(--force -f)'{-f,--force}'[ignore safety measures]' \
+}
+
 _hg_cmd_serve() {
   _arguments -s -w : $_hg_global_opts \
   '(--accesslog -A)'{-A+,--accesslog}'[name of access log file]:log file:_files' \