Add --autogenerateVersionNumber option to bump-oss-version.js

[amgleitman]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

Add an --autogenerateVersionNumber flag to scripts/bump-oss-version.js.

Some CI checks have been failing due to a change in this script. We still have some old invocations that assume the script will generate an ad-hoc version number. This change helps make the transition easier. If we so desire, we can change our CI scripts as needed in the future.

[acoates-ms]

Can we just use the nightly flag for this?

[amgleitman]

Can we just use the nightly flag for this?

Possibly, but I figure that adding a separate flag shows a clearer distinction between us and upstream.

[acoates-ms]

Ok, Then make sure to update the use of this script in the publish.yml when porting this to the main branch.