tests/test-merge-subrepos.t

revset: get revision number of each node from target namespaces

Before this patch, revset predicate "named()" uses each nodes gotten
from target namespaces directly.

This causes problems below:

  - combination of other predicates doesn't work correctly, because
    they assume that revisions are listed up in number

  - "hg log" doesn't show any revisions for "named()" result, because:

    - "changeset_printer" stores formatted output for each revisions
      into dict with revision number (= ctx.rev()) as a key of them

    - "changeset_printer.flush(rev)" writes stored output for
      the specified revision, but

    - "commands.log" invokes it with the node, gotten from "named()"

  - "hg debugrevspec" shows nodes (= may be binary) directly

Difference between revset predicate "tag()" and "named('tags')" in
tests is fixed in subsequent patch.

  $ hg init

  $ echo a > a
  $ hg ci -qAm 'add a'

  $ hg init subrepo
  $ echo 'subrepo = http://example.net/libfoo' > .hgsub
  $ hg ci -qAm 'added subrepo'

  $ hg up -qC 0
  $ echo ax > a
  $ hg ci -m 'changed a'
  created new head

  $ hg up -qC 1
  $ cd subrepo
  $ echo b > b
  $ hg add b
  $ cd ..

Should fail, since there are added files to subrepo:

  $ hg merge
  abort: uncommitted changes in subrepository 'subrepo'
  [255]