Add config to truncate commit hashes when copying them to the clipboard (#3402)

- **PR Description**

I often copy hashes in the commits panel in order to paste them into
Github comments (or other places), and I can't stand it when they have
the full length.

I picked a default of 12 for this; I find this to be a good middle
ground between being reliable in large repos (12 still works in the
linux kernel repo today, but it might not be enough in really huge
repos) and not being too ugly (many smaller repos can probably get away
with less).

0 files changed, 0 insertions, 0 deletions