When testing your apps with TestFlight, it's good to set newer build version when uploading another version, because it helps to differentiate between them and also if you use takeOff: message using their API, user with an old version, will see a message informing that there's a new version to download.

One query to Google, and we have a automatic solution. It's great, but it could use PROJECT_NAME setting, to locate plist file, so it works in every project without changing (also Xcode now uses CFBundleVersion instead of CWBuildNumber):

buildNumber=$(/usr/libexec/PlistBuddy -c "Print CFBundleVersion" ${PROJECT_DIR}/${PROJECT_NAME}/${PROJECT_NAME}-Info.plist)
buildNumber=$(($buildNumber + 1))
/usr/libexec/PlistBuddy -c "Set :CFBundleVersion $buildNumber" ${PROJECT_DIR}/${PROJECT_NAME}/${PROJECT_NAME}-Info.plist

Now just add "Run Script" build phase with this script (remember to move it before "Copy Bundle Resources" phase) and set your CFBundleVersion to an integer.