Merge branch 'jn/editor-pager'

Merge branch 'jn/editor-pager'

* jn/editor-pager:
  Provide a build time default-pager setting
  Provide a build time default-editor setting
  am -i, git-svn: use "git var GIT_PAGER"
  add -i, send-email, svn, p4, etc: use "git var GIT_EDITOR"
  Teach git var about GIT_PAGER
  Teach git var about GIT_EDITOR
  Suppress warnings from "git var -l"
  Do not use VISUAL editor on dumb terminals
  Handle more shell metacharacters in editor names