Integrate a build phase that checks if Manifest.lock is in sync

[stigi]

As discussed on the mailing list.

This adds a build phase to the Applications target that checks if Pods/Manifest.lock is in sync with Podfile.lock. This helps to inform developers of updating their Pods when the Pods directory is not tracked by version control.

[stigi]

Started this PR of the 0.17.2 tag since master specs would fail all over me.

[fabiopelosin]

Solid work! Thanks.

[fabiopelosin]

@stigi Please, let me know if you would like to be more involved with CP and would like to have commit access.

[stigi]

@irrationalfab will continue opening pull requests for now. Maybe at a later point in time. Thanks!

[fabiopelosin]

For those reading this thread. Projects which already have been integrated with CocoaPods will not be upgraded automatically (for the time being). To implement this feature manually you can:

1. Create for your target a shell script build phase named Check Pods Manifest.lock

2. Configure it to run the following bash script:

   diff "${PODS_ROOT}/../Podfile.lock" "${PODS_ROOT}/Manifest.lock" > /dev/null
   if [[ $? != 0 ]] ; then
       cat << EOM
   Podfile.lock and Manifest.lock are not in sync.
   You might need to run a \`pod install\`.
   EOM
       exit 1
   fi
   

[nikolaykasyanov]

Shouldn't message be changed from "You might need to run a pod install" to "You might need to run a pod install or to update your CocoaPods"? because CocoaPods version saved in lockfiles too.

[fabiopelosin]

@Corristo 👍 Will you submit a pull request?

[nikolaykasyanov]

@irrationalfab I'll try ;)

[fabiopelosin]

@Corristo This is awesome! Please let me know if you need any support.