While a user project is open and we delete/change the xcconfig files which
the user project references. It causes any subsequent builds to fail
until the project is closed/re-opened, or the project file is touched.

This commit touches the file if we do not need to save it, thus causing
Xcode to reload it.

Closes #2627
Closes #2665

Closes https://github.com/CocoaPods/CocoaPods/issues/2494.

Fixes #2631.

[Command] Remove deprecated pod push

Closes https://github.com/CocoaPods/CocoaPods/issues/2624.

Remove duplicated "because" word in warning message.

Fix for 52c2f915.

Update to new CLIntegracon Patch

[CHANGELOG] Add changlog entry for sanitization of special characters in build configs in target environment header

CHANGELOG entry for https://github.com/CocoaPods/CocoaPods/pull/2532.

Spec for changes introduced in https://github.com/CocoaPods/CocoaPods/pull/2532

Configuration specific preprocessor definition can generate a lot of warning

Use a var instead, as per @alloy

Especially warn a user in the case of a RC version.

Addresses a regression introduced in https://github.com/CocoaPods/CocoaPods/pull/2601

[TargetIntegrator] Ensures that the user project is not saved when there are no user targets integrated.

[Resolver] Added tests, notice if the required version exists in multiple sources (CocoaPods/CocoaPods#2556)

Fixes https://github.com/CocoaPods/CocoaPods/issues/2591

[TargetIntegrator] Ensures that the user project is not saved when there are no user targets integrated.

[TargetIntegrator] Ensures that the user project is not saved when there are no user targets integrated.

Remove references to Source#data_provider