Merge branch 'la/tag-force-signing-annotated-tags'

Merge branch 'la/tag-force-signing-annotated-tags'

"git tag" can create an annotated tag without explicitly given an
"-a" (or "-s") option (i.e. when a tag message is given).  A new
configuration variable, tag.forceSignAnnotated, can be used to tell
the command to create signed tag in such a situation.

* la/tag-force-signing-annotated-tags:
  tag: add the option to force signing of annotated tags