use git2u from IUS to support GIT_SSH_COMMAND
use git2u from IUS to support GIT_SSH_COMMAND

tbretl/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,parasgithub/PrairieLearn,parasgithub/PrairieLearn,rbessick5/PrairieLearn,rbessick5/PrairieLearn,mwest1066/PrairieLearn,mwest1066/PrairieLearn,rbessick5/PrairieLearn,rbessick5/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,rbessick5/PrairieLearn,tbretl/PrairieLearn,mwest1066/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,mwest1066/PrairieLearn,mwest1066/PrairieLearn