git-debrebase(1): document convert-from-gbp

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/git-debrebase b/git-debrebase
index 2520d52c5555f501eabd241b73393874c7d68294..fc60a76cd76e72a7209325c56a1623263c3b0969 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -25,7 +25,6 @@
 #    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:

diff --git a/git-debrebase.1.pod b/git-debrebase.1.pod
index ce442dafad0ead2dfd91bcdf371d20c5187d8cf0..40c8081485efddce3f71029c68d6f1075dd3e8f5 100644 (file)
--- a/git-debrebase.1.pod
+++ b/git-debrebase.1.pod
@@ -155,6 +155,38 @@ that its command line syntax is optimal.
 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