rebase: test to show brokenness with requiredest

As shown in issue5513, --continue is broken when destination is required. This
adds a patch that demonstates this silly behavior, which will be fixed in a
future patch.

tests/test-rebase-dest.t

@@ -1,33 +1,60 b''
 Require a destination
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > rebase =
   > [commands]
   > rebase.requiredest = True
   > EOF
   $ hg init repo
   $ cd repo
   $ echo a >> a
   $ hg commit -qAm aa
   $ echo b >> b
   $ hg commit -qAm bb
   $ hg up ".^"
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ echo c >> c
   $ hg commit -qAm cc
   $ hg rebase
   abort: you must specify a destination
   (use: hg rebase -d REV)
   [255]
   $ hg rebase -d 1
   rebasing 2:5db65b93a12b "cc" (tip)
   saved backup bundle to $TESTTMP/repo/.hg/strip-backup/5db65b93a12b-4fb789ec-backup.hg (glob)
   $ hg rebase -d 0 -r . -q
   $ HGPLAIN=1 hg rebase
   rebasing 2:889b0bc6a730 "cc" (tip)
   saved backup bundle to $TESTTMP/repo/.hg/strip-backup/889b0bc6a730-41ec4f81-backup.hg (glob)
   $ hg rebase -d 0 -r . -q
   $ hg --config commands.rebase.requiredest=False rebase
   rebasing 2:279de9495438 "cc" (tip)
   saved backup bundle to $TESTTMP/repo/.hg/strip-backup/279de9495438-ab0a5128-backup.hg (glob)
 
+Requiring dest should not break continue or other rebase options
+  $ hg up 1 -q
+  $ echo d >> c
+  $ hg commit -qAm dc
+  $ hg log -G -T '{rev} {desc}'
+  @  3 dc
+  |
+  | o  2 cc
+  |/
+  o  1 bb
+  |
+  o  0 aa
+  
+  $ hg rebase -d 2
+  rebasing 3:0537f6b50def "dc" (tip)
+  merging c
+  warning: conflicts while merging c! (edit, then use 'hg resolve --mark')
+  unresolved conflicts (see hg resolve, then hg rebase --continue)
+  [1]
+  $ echo d > c
+  $ hg resolve --mark --all
+  (no more unresolved files)
+  continue: hg rebase --continue
+  $ hg rebase --continue
+  abort: you must specify a destination
+  (use: hg rebase -d REV)
+  [255]