[historyView] Show date columns in local time zone, original on hover

The local time zone makes sense to the user as they can compare the
different commit dates much easier, and it is what is shown in other
places of the UI as well.

On hover, the full date in original time zone is shown in ISO format.

Bug: 369802
Change-Id: I4b0b19dfa8e3c51efc21ff394a84f891c6f72113
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
[historyView] Show name and email on hover of author/committer column

Change-Id: I430857cfafe72942b045d06dcdc6fee0259c0c52
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
[stagingView] Compare against HEAD for conflicting files

Previously, the first index entry was used (base stage, content of file
in common ancestor), which is confusing. Comparing against HEAD is more
sensible in that case.

Bug: 427054
Change-Id: I186448f79ff1d8a416a985543138ba8715a7705a
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>