fix baseRevision for Rage's VcsInfoCollector
fix baseRevision for Rage's VcsInfoCollector

Summary:
While making changing in the way we collect the VCS info I made a mistake and
made rage pick up changed files and the baseRevisionId like when we execute
normal commands. This is wrong because in rage we want to get the diff between
the current status and the base revision. This diff addresses this issue.

Test Plan:
* CI
* manual testing of buck rage

Reviewed By: Coneko

fbshipit-source-id: 9df84a6

daedric/buck,Addepar/buck,vschs007/buck,LegNeato/buck,robbertvanginkel/buck,davido/buck,SeleniumHQ/buck,justinmuller/buck,rmaz/buck,robbertvanginkel/buck,zhan-xiong/buck,LegNeato/buck,shs96c/buck,Addepar/buck,shybovycha/buck,Addepar/buck,JoelMarcey/buck,k21/buck,k21/buck,LegNeato/buck,ilya-klyuchnikov/buck,sdwilsh/buck,darkforestzero/buck,clonetwin26/buck,dsyang/buck,LegNeato/buck,daedric/buck,shybovycha/buck,ilya-klyuchnikov/buck,ilya-klyuchnikov/buck,JoelMarcey/buck,zhan-xiong/buck,rmaz/buck,shs96c/buck,justinmuller/buck,SeleniumHQ/buck,Addepar/buck,vschs007/buck,zhan-xiong/buck,Addepar/buck,k21/buck,justinmuller/buck,SeleniumHQ/buck,darkforestzero/buck,daedric/buck,facebook/buck,brettwooldridge/buck,Addepar/buck,shybovycha/buck,darkforestzero/buck,nguyentruongtho/buck,davido/buck,rmaz/buck,grumpyjames/buck,kageiit/buck,JoelMarcey/buck,dsyang/buck,SeleniumHQ/buck,romanoid/buck,kageiit/buck,shybovycha/buck,ilya-klyuchnikov/buck,shybovycha/buck,darkforestzero/buck,k21/buck,robbertvanginkel/buck,daedric/buck,vschs007/buck,dsyang/buck,ilya-klyuchnikov/buck,zpao/buck,rmaz/buck,marcinkwiatkowski/buck,Addepar/buck,JoelMarcey/buck,LegNeato/buck,marcinkwiatkowski/buck,shybovycha/buck,ilya-klyuchnikov/buck,facebook/buck,sdwilsh/buck,k21/buck,marcinkwiatkowski/buck,nguyentruongtho/buck,sdwilsh/buck,JoelMarcey/buck,davido/buck,romanoid/buck,k21/buck,kageiit/buck,shs96c/buck,SeleniumHQ/buck,zhan-xiong/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,justinmuller/buck,rmaz/buck,romanoid/buck,clonetwin26/buck,Addepar/buck,SeleniumHQ/buck,Addepar/buck,marcinkwiatkowski/buck,sdwilsh/buck,justinmuller/buck,darkforestzero/buck,clonetwin26/buck,romanoid/buck,zhan-xiong/buck,grumpyjames/buck,shs96c/buck,kageiit/buck,shybovycha/buck,brettwooldridge/buck,ilya-klyuchnikov/buck,vschs007/buck,davido/buck,brettwooldridge/buck,Addepar/buck,shs96c/buck,marcinkwiatkowski/buck,kageiit/buck,shs96c/buck,davido/buck,romanoid/buck,dsyang/buck,vschs007/buck,justinmuller/buck,romanoid/buck,robbertvanginkel/buck,grumpyjames/buck,darkforestzero/buck,JoelMarcey/buck,clonetwin26/buck,zpao/buck,justinmuller/buck,davido/buck,sdwilsh/buck,robbertvanginkel/buck,daedric/buck,zhan-xiong/buck,LegNeato/buck,clonetwin26/buck,LegNeato/buck,vschs007/buck,darkforestzero/buck,brettwooldridge/buck,romanoid/buck,clonetwin26/buck,brettwooldridge/buck,shs96c/buck,SeleniumHQ/buck,brettwooldridge/buck,romanoid/buck,facebook/buck,daedric/buck,romanoid/buck,clonetwin26/buck,marcinkwiatkowski/buck,rmaz/buck,grumpyjames/buck,brettwooldridge/buck,LegNeato/buck,marcinkwiatkowski/buck,dsyang/buck,nguyentruongtho/buck,shs96c/buck,clonetwin26/buck,davido/buck,clonetwin26/buck,romanoid/buck,shybovycha/buck,marcinkwiatkowski/buck,vschs007/buck,davido/buck,nguyentruongtho/buck,zhan-xiong/buck,Addepar/buck,vschs007/buck,JoelMarcey/buck,Addepar/buck,romanoid/buck,k21/buck,daedric/buck,shybovycha/buck,SeleniumHQ/buck,nguyentruongtho/buck,daedric/buck,k21/buck,sdwilsh/buck,rmaz/buck,LegNeato/buck,grumpyjames/buck,shs96c/buck,daedric/buck,SeleniumHQ/buck,LegNeato/buck,vschs007/buck,daedric/buck,facebook/buck,dsyang/buck,JoelMarcey/buck,zpao/buck,marcinkwiatkowski/buck,vschs007/buck,robbertvanginkel/buck,darkforestzero/buck,marcinkwiatkowski/buck,SeleniumHQ/buck,darkforestzero/buck,zhan-xiong/buck,SeleniumHQ/buck,JoelMarcey/buck,zhan-xiong/buck,SeleniumHQ/buck,justinmuller/buck,brettwooldridge/buck,JoelMarcey/buck,LegNeato/buck,grumpyjames/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,shs96c/buck,ilya-klyuchnikov/buck,nguyentruongtho/buck,justinmuller/buck,shs96c/buck,sdwilsh/buck,romanoid/buck,rmaz/buck,dsyang/buck,rmaz/buck,zpao/buck,dsyang/buck,vschs007/buck,grumpyjames/buck,sdwilsh/buck,marcinkwiatkowski/buck,zhan-xiong/buck,sdwilsh/buck,ilya-klyuchnikov/buck,rmaz/buck,dsyang/buck,grumpyjames/buck,robbertvanginkel/buck,brettwooldridge/buck,robbertvanginkel/buck,vschs007/buck,kageiit/buck,darkforestzero/buck,daedric/buck,rmaz/buck,dsyang/buck,zhan-xiong/buck,daedric/buck,shybovycha/buck,marcinkwiatkowski/buck,sdwilsh/buck,zhan-xiong/buck,JoelMarcey/buck,sdwilsh/buck,Addepar/buck,clonetwin26/buck,dsyang/buck,sdwilsh/buck,grumpyjames/buck,clonetwin26/buck,robbertvanginkel/buck,zhan-xiong/buck,justinmuller/buck,robbertvanginkel/buck,zpao/buck,k21/buck,davido/buck,grumpyjames/buck,robbertvanginkel/buck,k21/buck,shybovycha/buck,nguyentruongtho/buck,zpao/buck,facebook/buck,shs96c/buck,dsyang/buck,grumpyjames/buck,grumpyjames/buck,justinmuller/buck,k21/buck,facebook/buck,facebook/buck,brettwooldridge/buck,vschs007/buck,darkforestzero/buck,ilya-klyuchnikov/buck,davido/buck,k21/buck,kageiit/buck,justinmuller/buck,darkforestzero/buck,LegNeato/buck,romanoid/buck,dsyang/buck,justinmuller/buck,brettwooldridge/buck,clonetwin26/buck,JoelMarcey/buck,ilya-klyuchnikov/buck,robbertvanginkel/buck,shybovycha/buck,rmaz/buck,sdwilsh/buck,shybovycha/buck,ilya-klyuchnikov/buck,davido/buck,JoelMarcey/buck,brettwooldridge/buck,LegNeato/buck,davido/buck,zpao/buck,clonetwin26/buck,daedric/buck,k21/buck,davido/buck,rmaz/buck,brettwooldridge/buck,darkforestzero/buck,shs96c/buck