bash_completion: Add completion for cros_portage_upgrade

BUG=none
TEST=cros_portage_upgrade --<tab><tab>
TEST=cros_portage_upgrade --board=<tab><tab>
TEST=cros_portage_upgrade --upg<tab>

Change-Id: Iff7abeb5a6d673a50b29f15158768262f9288e0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1904301
Tested-by: Craig Hesling <hesling@chromium.org>
Commit-Queue: Craig Hesling <hesling@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/bash_completion b/bash_completion
index a0d6232..ac184c2 100644
--- a/bash_completion
+++ b/bash_completion
@@ -252,6 +252,13 @@
   return 0
 }
 
+_cros_portage_upgrade() {
+  COMPREPLY=()
+  _flag_complete && return 0
+  _complete_board_sysroot_flag && return 0
+  return 0
+}
+
 # Complete equery's <module-name> argument.
 _complete_equery_module_name() {
   [ ${COMP_CWORD} -eq 1 ] || return 1
@@ -279,6 +286,8 @@
 complete -o bashdefault -o default -o nospace -F _test_that_complete test_that
 complete -F _cros cros
 complete -F _cros_workon cros_workon
+complete -o bashdefault -o default -o nospace -F _cros_portage_upgrade \
+            cros_portage_upgrade
 complete -o bashdefault -o default -F _complete_equery equery
 
 # Use equery completion for equery-$board for known boards