Add further vertex attributes for artifact vertices

[clhunsen]

Description

Related to the idea to add further vertex attributes (see issue #92), we should provide some further vertex attributes for artifact vertices. Currently, we only provide vertex attributes for commits, but we should definitely provide functions to add attributes for e-mails and issues.

The idea for this originates here.

Motivation

The motivation for this enhancement is basically the proper alignment of functionality for all types of artifact vertices. If we have any information that would fit, we should provide corresponding functionality by means of new vertex-attribute functions.

Ideas for the Implementation

Some ideas for further vertex attributes proposed in this issue:

• Mail threads
  • Number of contributors to this thread
  • Number of e-mails in this thread
  • Start and end date
  • Originating mailing list
• Issue threads
  • Number of contributors to this issue
  • Number of events or comments in this issue
  • Start and end date
  • Issue Title
  • Is Pull Request
  • Maybe it could also be interesting for pull requests to know whether they are merged/closed/open?

What are your thoughts?