rebase: add potential divergent commit hashes to error message (issue5086)

hgext/rebase.py

@@ -307,10 +307,13 b' def rebase(ui, repo, **opts):'
                 divergencebasecandidates = rebaseobsrevs - rebaseobsskipped
 
                 if divergencebasecandidates and not divergenceok:
-                    msg = _("this rebase will cause divergence")
+                    divhashes = (str(repo[r])
+                                 for r in divergencebasecandidates)
+                    msg = _("this rebase will cause "
+                            "divergences from: %s")
                     h = _("to force the rebase please set "
                           "rebase.allowdivergence=True")
-                    raise error.Abort(msg, hint=h)
+                    raise error.Abort(msg % (",".join(divhashes),), hint=h)
 
                 # - plain prune (no successor) changesets are rebased
                 # - split changesets are not rebased if at least one of the

tests/test-rebase-obsolete.t

@@ -771,7 +771,7 b' If a rebase is going to create divergenc'
   phases: 8 draft
   unstable: 1 changesets
   $ hg rebase -s 10 -d 12
-  abort: this rebase will cause divergence
+  abort: this rebase will cause divergences from: 121d9e3bc4c6
   (to force the rebase please set rebase.allowdivergence=True)
   [255]
   $ hg log -G