Before a branch is deleted, we check that it points to a valid
commit. With -d we also check that the commit is a merged; this
check is not done with -D.
The reason for that is that commits pointed to by branches should
never go missing; if they do then something broke and it's better
to stop instead of adding to the mess. And a non-merged commit
may contain changes that are worth preserving, so we require the
stronger option -D instead of -d to get rid of them.
If a branch consists of a symref, these concerns don't apply.
Deleting such a branch can't make a commit become unreferenced,
so we don't need to check if it is merged, or even if it is
actually a valid commit. Skip them in that case. This allows
us to delete dangling symref branches.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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