Steps:
1. open new 3D project
2. window > package manager
3. + > git url
4. enter a valid format forPackMan git url (like https://github.com/Unity-Technologies/Graphics.git?path=/com.unity.render-pipelines.core#c565117a2232f99475250c303c07d158328fe636 )
5. click add
6. observe no progress bar or indication of work happening
7. modify Packages/manifest.json
8. return to editor window
9. observe attempt to reload and error in console
10. close editor to kill git clone

Expected: progress bar and cancel button to indicate git clone is happening via PackMan
Actual: no indication or option to cancel the clone if you want to make any changes to manifest.json in meantime

Repro: 2020.1.0b7, 2020.2.0a9

Note: background tasks can show progress bar in bottom-right corner window (see 2020.2 video)