Be able to configure the number of threads for git submodules update (#3438)
Be able to configure the number of threads for git submodules update (#3438)

* make the number of submodule update threads configurable

* change thread number to be a script argument

erkyrath/linguist,tschf/linguist,github/linguist,JJ/linguist,JJ/linguist,yyx990803/linguist,pchaigno/linguist,sebgod/linguist,yyx990803/linguist,MahmoudFayed/linguist,yyx990803/linguist,yyx990803/linguist,erkyrath/linguist,mwpastore/linguist,R4PaSs/linguist,stanhu/linguist,tschf/linguist,erkyrath/linguist,erkyrath/linguist,MahmoudFayed/linguist,sebgod/linguist,stanhu/linguist,christop/linguist,github/linguist,stanhu/linguist,github/linguist,sebgod/linguist,stanhu/linguist,github/linguist,pchaigno/linguist,pchaigno/linguist,mwpastore/linguist,pchaigno/linguist,R4PaSs/linguist,christop/linguist,JJ/linguist,sebgod/linguist,JJ/linguist