fsck only checks battery when requested, which is not by default.

This fixes having JFS as the root partition on battery power.
For most modern FS's this is a non op, or a very small op by default
so it should be fine.
Fixes Gentoo #291654.

conf.d/fsck

@@ -13,6 +13,11 @@
 #fsck_passno=">1"
 #fsck_passno="<2"
 
+# Most modern fs's don't require a full fsck on boot, but for those that do
+# it may be adivisable to skip this when running on battery.
+# WARNING: Do not turn this off if you have any JFS partitions.
+fsck_on_battery="YES"
+
 # fsck_shutdown causes fsck to trigger during shutdown as well as startup.
 # The end result of this is that if any periodic non-root filesystem checks are
 # scheduled, under normal circumstances the actual check will happen during

init.d/fsck.in

@@ -73,7 +73,7 @@ start()
 	if _forcefsck; then
 		fsck_opts="$fsck_opts -f"
 		check_extra="(check forced)"
-	elif ! _on_ac_power; then
+	elif ! yesno ${fsck_on_battery:-YES} && ! _on_ac_power; then
 		ewarn "Skipping fsck due to not being on AC power"
 		return 0
 	fi