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