Help with parsing a unorganized file

Shell Programming and Scripting
1

I have a file which is of this format

ABCD1
,1,22,green,2013-02-14,09:00:00,true
,1,22,red,2013-02-14,09:00:00,true
,1,22,blue,2013-02-14,09:00:00,true
ABCD2
,1,22,yellow,2013-02-14,09:00:00,true
,1,22,white,2013-02-14,09:00:00,true
,1,22,blue,2013-02-14,09:00:00,true
ABCD3
,1,22,black,2013-02-14,09:00:00,true
,1,22,pink,2013-02-14,09:00:00,true

I want to generate a file as below using unix commands

ABCD1,1,22,green,2013-02-14,09:00:00,true
ABCD1,1,22,red,2013-02-14,09:00:00,true
ABCD1,1,22,blue,2013-02-14,09:00:00,true
ABCD2,1,22,yellow,2013-02-14,09:00:00,true
ABCD2,1,22,white,2013-02-14,09:00:00,true
ABCD2,1,22,blue,2013-02-14,09:00:00,true
ABCD3,1,22,black,2013-02-14,09:00:00,true
ABCD3,1,22,pink,2013-02-14,09:00:00,true
2 
awk '!/^,/{h=$1}/^,/{print h $0}' file