# git-debrebase [<options>] launder-v0 # prints breakwater tip etc.
# git-debrebase [<options>] downstream-rebase-launder-v0 # experimental
#
-# git-debrebase [<options>] convert-from-gbp [<upstream-git-rev>]
# git-debrebase [<options>] convert-to-gbp
# problems / outstanding questions:
We may want to introduce an incompatible replacement syntax
under the name C<new-upstream>.
+=item git-debrebase convert-from-gbp [<upstream-commitish>]
+
+Cnnverts a gbp patches-unapplied branch
+(not a gbp pq patch queue branch)
+into a git-debrebase interchange branch.
+
+This is done by generating a new anchor merge,
+converting the quilt patches as a delta queue,
+and dropping the patches from the tree.
+
+The upstream commitish should correspond to
+the gbp upstream branch.
+It is a problem if it is not an ancestor of HEAD,
+or if the history between the upstream and HEAD
+contains commits which make changes to upstream files.
+
+It is also a problem if the specified upstream
+has a debian/ subdirectory.
+This check exists to detect certain likely user errors,
+but if this situation is true and expected,
+forcing it is fine.
+
+The result is a well-formed git-debrebase interchange branch.
+The result is also fast-forward from the gbp branch.
+
+Note that it is dangerous not to know whether you are
+dealing with a gbp patches-unappled branch containing quilt patches,
+or a git-debrebase interchange branch.
+At worst,
+using the wrong tool for the branch format might result in
+a dropped patch queue!
+
=back
=head1 UNDERLYING AND SUPPLEMENTARY OPERATIONS