d29e7cc00b26 introduced a number of issues:

* The src-link line for $GITHUB_WORKSPACE in feeds.conf is overridden.

* The base feed is missing.

* Any branch/tag/commit information in feeds.conf.default is omitted,
  i.e. each feed's master branch is always used.

This fixes all of these issues.

Fixes: d29e7cc00b26 ("Use feeds from GH mirror for GH actions")
Signed-off-by: Jeffery To <[email protected]>