csl sbt build: Use git rev-parse instead of symbolic-ref
csl sbt build: Use git rev-parse instead of symbolic-ref

Problem

sbt build calls 'git symbolic-ref' which fails in a detached HEAD state. This breaks github travis builds, e.g. https://travis-ci.org/twitter/util/jobs/52793532

Solution

Use 'git rev-parse --abbrev HEAD' instead.

RB_ID=596030

Krasnyanskiy/finagle,mkhq/finagle,liamstewart/finagle,luciferous/finagle,nkhuyu/finagle,nomadlabs/finagle,bruceluo/finagle,svetlyak40wt/finagle,cogitate/twitter-finagle-uuid,travisbrown/finagle,folone/finagle,kumasento/finagle,nomadlabs/finagle,twitter/finagle,liamstewart/finagle,kumasento/finagle,lysu/finagle,koshelev/finagle,nomadlabs/finagle,rjbhewei/finagle,luciferous/finagle,kingtang/finagle,jeremyrsmith/finagle,mkhq/finagle,lucaslanger/finagle,a-manumohan/finagle,liamstewart/finagle,sveinnfannar/finagle,rojanu/finagle,zfy0701/finagle,nomadlabs/finagle,almendar/finagle,spockz/finagle,rojanu/finagle,lysu/finagle,scorpiovn/finagle,lucaslanger/finagle,koshelev/finagle,mosesn/finagle,BuoyantIO/finagle,OopsOutOfMemory/finagle,Krasnyanskiy/finagle,jeremyrsmith/finagle,latur19318/finagle,twitter/finagle,travisbrown/finagle,jay-johnson/finagle,jpederzolli/finagle,bruceluo/finagle,jpederzolli/finagle,jay-johnson/finagle,chen0031/finagle,adriancole/finagle,bruceluo/finagle,chen0031/finagle,latur19318/finagle,BuoyantIO/finagle,lucaslanger/finagle,folone/finagle,scorpiovn/finagle,Krasnyanskiy/finagle,a-manumohan/finagle,nkhuyu/finagle,kumasento/finagle,chen0031/finagle,latur19318/finagle,spockz/finagle,travisbrown/finagle,suls/finagle,lukiano/finagle,luciferous/finagle,rjbhewei/finagle,cogitate/twitter-finagle-uuid,zfy0701/finagle,mosesn/finagle,suls/finagle,lysu/finagle,sveinnfannar/finagle,jay-johnson/finagle,rjbhewei/finagle,luciferous/finagle,mkhq/finagle,rojanu/finagle,jeremyrsmith/finagle,twitter/finagle,liamstewart/finagle,cogitate/twitter-finagle-uuid,lukiano/finagle,adriancole/finagle,scorpiovn/finagle,spockz/finagle,nkhuyu/finagle,nkhuyu/finagle,nomadlabs/finagle,rodrigodealer/finagle,chen0031/finagle,OopsOutOfMemory/finagle,koshelev/finagle,BuoyantIO/finagle,a-manumohan/finagle,BuoyantIO/finagle,thirstycrow/finagle,zfy0701/finagle,thirstycrow/finagle,chen0031/finagle,Krasnyanskiy/finagle,jeremyrsmith/finagle,koshelev/finagle,luciferous/finagle,zfy0701/finagle,mosesn/finagle,jay-johnson/finagle,rojanu/finagle,mosesn/finagle,lukiano/finagle,spockz/finagle,almendar/finagle,jpederzolli/finagle,latur19318/finagle,adriancole/finagle,adriancole/finagle,kingtang/finagle,sveinnfannar/finagle,zfy0701/finagle,thirstycrow/finagle,OopsOutOfMemory/finagle,folone/finagle,thirstycrow/finagle,jeremyrsmith/finagle,spockz/finagle,Krasnyanskiy/finagle,OopsOutOfMemory/finagle,suls/finagle,jay-johnson/finagle,suls/finagle,rodrigodealer/finagle,mosesn/finagle,spockz/finagle,mkhq/finagle,kumasento/finagle,rodrigodealer/finagle,almendar/finagle,koshelev/finagle,lucaslanger/finagle,scorpiovn/finagle,mkhq/finagle,jpederzolli/finagle,cogitate/twitter-finagle-uuid,svetlyak40wt/finagle,fengshao0907/finagle,lukiano/finagle,rodrigodealer/finagle,luciferous/finagle,rjbhewei/finagle,almendar/finagle,bruceluo/finagle,lysu/finagle,folone/finagle,lysu/finagle,kingtang/finagle,fengshao0907/finagle,folone/finagle,kingtang/finagle,koshelev/finagle,almendar/finagle,rodrigodealer/finagle,travisbrown/finagle,fengshao0907/finagle,fengshao0907/finagle,BuoyantIO/finagle,nkhuyu/finagle,a-manumohan/finagle,lukiano/finagle,adriancole/finagle,cogitate/twitter-finagle-uuid,fengshao0907/finagle,rojanu/finagle,OopsOutOfMemory/finagle,rjbhewei/finagle,twitter/finagle,svetlyak40wt/finagle,travisbrown/finagle,jpederzolli/finagle,BuoyantIO/finagle,liamstewart/finagle,kumasento/finagle,thirstycrow/finagle,scorpiovn/finagle,a-manumohan/finagle,sveinnfannar/finagle,lukiano/finagle,sveinnfannar/finagle,mkhq/finagle,svetlyak40wt/finagle,sveinnfannar/finagle,kingtang/finagle,adriancole/finagle,suls/finagle,twitter/finagle,svetlyak40wt/finagle,latur19318/finagle,lucaslanger/finagle,bruceluo/finagle