commit-graph: avoid message Computing commit graph generation numbers...

[ryenus <ryenus@xxxxxxxxx>]

Hi,

After setting fetch.writeCommitGraph to true, the message
> Computing commit graph generation numbers: 100% (2/2), done.
is always printed.

IMHO this is internal to Git and probably NOT necessary to print by
default, if really necessary, maybe an option can be provided
to turn it on. Thoughts?

Thanks