|  | Dart SDK dependency | 
|  | =================== | 
|  |  | 
|  | The `bin/internal/engine.version` file controls which version of the Flutter engine to use. | 
|  | The file contains the commit hash of a commit in the <https://github.com/flutter/engine> repository. | 
|  | That hash must have successfully been compiled on <https://build.chromium.org/p/client.flutter/> and had its artifacts (the binaries that run on Android and iOS, the compiler, etc) successfully uploaded to Google Cloud Storage. | 
|  |  | 
|  | The `/bin/internal/engine.merge_method` file controls how we merge a pull | 
|  | request created by the engine auto-roller. If it's `squash`, there's only one | 
|  | commit for a pull request no matter how many engine commits there are inside | 
|  | that pull request. If it's `rebase`, the number of commits in the framework is | 
|  | equal to the number of engine commits in the pull request. The latter method | 
|  | makes it easier to detect regressions but costs more test resources. |