feat(FormController): add $rollbackViewValue to rollback all controls

[shahata]

Currently it is possible to use ngModelOptions to pend model updates until form is submitted, but in case the user wants to reset the form back to its original values he must call $rollbackViewValue on each input control in the form. This commit adds a $rollbackViewValue on the form controller in order to make this operation easier, similarly to $commitViewValue.

[mary-poppins]

Thanks for the PR! Please check the items below to help us merge this faster. See the contributing docs for more information.

• Uses the issue template (#7595)

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Thanks again for your help!

[rodyhaddad]

Do you have a use case for rolling back the pending values of the whole form?

[shahata]

@rodyhaddad - Yes, I think it is very useful in case ngModelOptions is used to commit the model only on form submit (and then the user can roll back the whole form easily from the reset button). Here's a plunkr example: http://plnkr.co/edit/yJOtCHYzc1Rsm85ihwZi?p=preview

You can compare that to how things are done without ngModelOptions today where you have to make a copy of the model on reset & update: https://docs.angularjs.org/guide/forms

[shahata]

@rodyhaddad what's your take on this? I think that this is a very important feature for ppl who use ngModelOptions to pend updates until the form is submitted...

[rodyhaddad]

Thought I had merged this after your response.
Thanks for pinging me about it!