* Change getInstance() (deprecated) to get()

* Reverting modifications according review

* Changing for use the variable

Just import changes, from hudson.model.Jenkins -> jenkins.model.Jenkins,
and Javadoc comments.
Signed-off-by: NNigel Magnay <nigel.magnay@gmail.com>

Signed-off-by: NNigel Magnay <nigel.magnay@gmail.com>

See:

  - SCM.compareRemoteRevisionWith
  - SCM.calcRevisionsFromBuild
  - SCMRevisionState

for details. This feature was originally developed in a branch,
whose merge records are as follows:

------------------

Merged revisions 24271,27060,27065,27083-27084 via svnmerge from 
https://www.dev.java.net/svn/hudson/branches/HUDSON-2180/main

........
  r24271 | kohsuke | 2009-11-30 19:41:30 -0800 (Mon, 30 Nov 2009) | 1 line
  
  committing my work in progress
........
  r27060 | kohsuke | 2010-02-05 18:11:05 -0800 (Fri, 05 Feb 2010) | 7 lines
  
  Made SVNRevisionState non-comparable, since doing so and distinguishing
  significant/insignificant changes is rather involving work.
  
  So that's why I originally opted for the compareRemoteRevisionWith method approach
  of telling SCM upfront about what it's comparing the state with.
........
  r27065 | kohsuke | 2010-02-06 08:49:50 -0800 (Sat, 06 Feb 2010) | 1 line
  
  crucial bug fix
........
  r27083 | kohsuke | 2010-02-06 10:37:46 -0800 (Sat, 06 Feb 2010) | 1 line
  
  doc improvement
........
  r27084 | kohsuke | 2010-02-06 10:39:50 -0800 (Sat, 06 Feb 2010) | 1 line
  
  doc improvement
........


git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@27103 71c3de6d-444a-0410-be80-ed276b4c234a

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@15081 71c3de6d-444a-0410-be80-ed276b4c234a

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@12491 71c3de6d-444a-0410-be80-ed276b4c234a