Merge branch 'da/gitk-reload-tag-contents'

After overwriting a tag with a new tag, "Reread references" action
in "gitk" correctly moved the marker in the display, but it failed
to discard a cached contents of the tag (even "Reload" didn't).

* da/gitk-reload-tag-contents:
  gitk: Rename 'tagcontents' to 'cached_tagcontent'
  gitk: Teach "Reread references" to reload tags
  gitk: Avoid Meta1-F5

diff --cc gitk-git/gitk
Simple merge