Support fetching from an upstream main git branch am: c0d933345f am: 797a4508bf am: 79148026df am: dd86cc541c

Original change: https://android-review.googlesource.com/c/platform/tools/external_updater/+/1705651

Change-Id: I2bb3244676d95f3acbead32f350e66784658a0d6