Merge branch 'jk/branch-l-0-deprecation'

Merge branch 'jk/branch-l-0-deprecation'

The "-l" option in "git branch -l" is an unfortunate short-hand for
"--create-reflog", but many users, both old and new, somehow expect
it to be something else, perhaps "--list".  This step warns when "-l"
is used as a short-hand for "--create-reflog" and warns about the
future repurposing of the it when it is used.

* jk/branch-l-0-deprecation:
  branch: deprecate "-l" option
  t: switch "branch -l" to "branch --create-reflog"
  t3200: unset core.logallrefupdates when testing reflog creation