chat: git push notification truncated

I just joined a team, created a new (thus empty) repository, and pushed a lot of commits to it. In the app (version 1.0.44_20180223200436+9a9ccec79-1 on archlinux) the group chat has a message ` pushed 19 commits to /master` listing the newest commits. There are however more than 19, so it should instead read "more than X commits" and/or end the list with something indicating that the added history is not shown in complete.

Reproduce this with an empty repository and a push containing more than 19 commits, then trace the group-chat git-push notification entry point in the Keybase client. Verify the notification clearly indicates that the commit history is truncated and that the displayed commit list is understandable.

Written by the indexing model from the issue text.