* Drop acknowledged mutations in schema migration (#1818)
Drop acknowledged mutations in schema migration as part of removing held write acks.
Port of firebase/firebase-js-sdk#1149
* Change removeMutationBatch to remove a single batch (#1955)
* Update Firestore Generated Protos
* Adding UnknownDocument and hasCommittedMutations (#1971)
* Removing held write batch handling from LocalStore (#1997)
* View changes for held write acks (#2004)
* Held Write Acks Unit Test Fixes (#2008)
* Held Write Ack Removal Spec Tests (#2018)
* Fix integration test
* remove conversions in `Local` and `Remote`
* replace `FSTSnapshotVersion` in `Model`
* replace `FSTSnapshotVersion` in the rest
* let test check equal with C++ equal
* fix newly added code
* address changes
* lint.sh now lints Objective-C++ too
* cpplint checks system-style includes that should be user-style
This prevents it from recognizing project sources as if they were C
system headers and then complaining that they're in the wrong place.
* cpplint checks #imports and #includes
* cpplint checks that C++ system headers aren't #imported
* cpplint checks for C system headers that could be C++ system headers
* cpplint checks that Objective-C sources include their headers
- FSTTimestamp is now FIRTimestamp, under Firestore/Source/{Public,API}. This is a temporary solution; eventually, FIRTimestamp is supposed to live somewhere under Firebase;
- move most internal Timestamp methods to the public header (the only exception is ISOString).
* Move all Firestore files to Objective-C++
* Update project file references
* Don't use module imports from Objective-C++
* Use extern "C" for C-accessible globals
* Work around more stringent type checking in Objective-C++
* NSMutableDictionary ivars aren't implicitly casted to NSDictionary
* FSTMaybeDocument callback can't be passed a function that accepts
FSTDocument
* NSComparisonResult can't be multiplied by -1 without casting
* Add a #include <inttypes.h> where needed
* Avoid using C++ keywords as variables
* Remove #if __cplusplus guards