update command only ever states the previous index state, but not the current one

[samuela]

Describe the bug
The (v2-)update command is great in that it gives the exact command necessary in order to revert to the previous package index state, but it doesn't actually say what state the package list just got update to. Adding this would be super useful info, esp. when trying to get exactly reproducible builds!

To Reproduce
Currently

$ cabal v2-update
Downloading the latest package list from hackage.haskell.org
To revert to previous state run:
    cabal v2-update 'hackage.haskell.org,2020-05-14T21:24:35Z'

Expected behavior

It would be great if we could get something like

$ cabal v2-update
Downloading the latest package list from hackage.haskell.org...

Updated package list to 'hackage.haskell.org,2020-05-14T21:24:35Z'!

To revert to previous state run:
    cabal v2-update 'hackage.haskell.org,2020-05-14T21:24:35Z'

System information

• Debian 9

ghc@bf86fd77bccf:~/out$ ./cabal --version
cabal-install version 3.2.0.0
compiled using version 3.2.0.0 of the Cabal library
ghc@bf86fd77bccf:~/out$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.8.3