tests: test that narrow preserves bookmarks on widen

When widening inserts older commits in the changelog, we have to
preserve bookmarks so they are not removed by the call to
repair.strip() we temporarily do. We didn't have any tests for that
before.

Differential Revision: https://phab.mercurial-scm.org/D5396

tests/test-narrow.t

@@ -237,6 +237,21 b" Narrowing doesn't resurrect old commits "
   0: add d0/f
   $ cd ..
 
+Widening doesn't lose bookmarks
+  $ hg clone --narrow ssh://user@dummy/master widen-bookmarks --include d0 -q
+  $ cd widen-bookmarks
+  $ hg bookmark my-bookmark
+  $ hg log -T "{rev}: {desc} {bookmarks}\n"
+  1: add d10/f my-bookmark
+  0: add d0/f 
+  $ hg tracked --addinclude d3 -q
+  $ hg log -T "{rev}: {desc} {bookmarks}\n"
+  3: add d10/f my-bookmark
+  2: add d3/f 
+  1: add d2/f 
+  0: add d0/f 
+  $ cd ..
+
 Can remove last include, making repo empty
   $ hg clone --narrow ssh://user@dummy/master narrow-empty --include d0 -r 5
   adding changesets