Let's try with backticks...

Let’s try again, this time with backticks…

begin
    a = "whatever"
end

… does this do “nice” curly quotes?

GIT=`xcrun -find git`
GIT_REV=`${GIT} rev-parse --short HEAD`
/usr/libexec/PlistBuddy -c "Set :REVISION ${GIT_REV}" "${SRCROOT}/{{path-to-your-info.plist-file}}"