Here we are getting all the refs except refs/changes. For some projects,
this is actually a very expensive operation to get all the refs and then
filter out the refs/changes (sicne there may be millions of refs/changes
and only thousands of other refs).
As proven by https://git.eclipse.org/r/c/jgit/jgit/+/173498/13, this
improves efficiency by a factor of 20 for larger projects to get all the
refs excluding refs/changes (instead of getting all refs and then
filtering out refs/changes).
Change-Id: I49b2c2829e2106fcc628445cc0a746039b5b5936
bf11e4f685