Update UPGRADING.md for v7 changes

Added upgrade notes for v7, including the reintroduction of options `create_branch`, `skip_fetch`, and `skip_checkout`, and updates to tagging options with the new `tag_name` parameter.

Author: stefanzweifel

UPGRADING.md

@@ -1,5 +1,12 @@
 # Upgrading
 
+## From v6 to v7
+
+The previously removed options `create_branch`, `skip_fetch`, and `skip_checkout` have been reintroduced in git-auto-commit v7. If you had removed these options from your workflows when upgrading to v6, you can now add them back if needed.
+
+Tagging a commit has been reworked. In addition to the existing `tagging_message`-option, a new `tag_name` option has been added. If you were using `tagging_message`, you can continue to do so, but if you want to specify a custom tag name and tag message, you can now use the `tag_name` and `tagging_message` option.
+(Specifying a `tagging_message` without a `tag_name` will create a tag with the name and message both set to the value of `tagging_message`.)
+
 ## From v5 to v6
 
 The following options have been removed from git-auto-commit and can be removed from your workflows.