fix bug in `get_commit` script.
fix bug in `get_commit` script.

MallabaevAzamat/FStar,YaccConstructor/FStar,YaccConstructor/FStar,hoheinzollern/FStar,MallabaevAzamat/FStar,MallabaevAzamat/FStar,hoheinzollern/FStar,FStarLang/FStar,A-Manning/FStar,YaccConstructor/FStar,YaccConstructor/FStar,MallabaevAzamat/FStar,A-Manning/FStar,A-Manning/FStar,FStarLang/FStar,FStarLang/FStar,hoheinzollern/FStar,hoheinzollern/FStar