Remove 'patch' link from tab, add to commit view

Remove 'patch' link from tab, add to commit view

It's a bit confusing to enter the patch view from the tab, since it has no
layout. And the commit view has always lacked showing the commit id. Both of
these warts are fixed by this commit, which adds a new header line in the
commit view which shows the commit id as a 'permalink' to the current commit
and also adds a link to the patch view of the current commit.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>