hooks/pre-auto-gc: adjust power checking for newer OS X

The output of "pmset -g batt" changed at some point from "Currently
drawing from 'AC Power'" to the slightly different "Now drawing from
'AC Power'". Starting the match from "drawing" makes the check work
in both old and new versions of OS X.

Signed-off-by: Panagiotis Astithas <pastith@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/hooks/pre-auto-gc-battery

@@ -33,7 +33,7 @@ elif grep -q "AC Power \+: 1" /proc/pmu/info 2>/dev/null
 then
 	exit 0
 elif test -x /usr/bin/pmset && /usr/bin/pmset -g batt |
-	grep -q "Currently drawing from 'AC Power'"
+	grep -q "drawing from 'AC Power'"
 then
 	exit 0
 fi