Git API does not declare GitAPIException call() and related cleanups

Git API does not declare GitAPIException call() and related cleanups

All commands should throw a GitAPIException so new exceptions can be
added without breaking the builds of old code, i.e. anyone that calls
a Git API should catch GitAPIException and not just the currently known
exceptions.

Now the only checked exceptions on Git API calls are GitException and
subclasses of it. New checked exceptions that are subclasses of
GitException may be added without breaking the API.

Javadoc for GitAPIException is declared on GitCommand and
inherited to subclasses. JGitInternalException is not explicitly
documented anymore.

Unfortunately this change itself breaks the API. The intention is
that it shall be possible to add new checked subclasses of
GitAPIException without breaking the API.

Bug: 366914
EGit-Change-Id: I50380f13fc82c22d0036f47c7859cc3a77e767c5
Change-Id: I50380f13fc82c22d0036f47c7859cc3a77e767c5
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>