tests/test-issue619.t

nodemap: only use persistent nodemap for non-inlined revlog

Revlog are inlined while they are small (to avoid having too many file to deal
with). The persistent nodemap will only provides a significant boost for large
enough revlog index. So it does not make sens to add an extra file to store
nodemap for small revlog.

We could consider inclining the nodemap data inside the revlog itself, but the
benefit is unclear so let it be an adventure for another time.

Differential Revision: https://phab.mercurial-scm.org/D7837

https://bz.mercurial-scm.org/619

  $ hg init
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ echo b > b
  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -Amb
  adding b

  $ hg co -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

Fast-forward:

  $ hg merge b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -Ammerge

Bogus fast-forward should fail:

  $ hg merge b
  abort: merging with a working directory ancestor has no effect
  [255]

Even with strange revset (issue4465)

  $ hg merge ::.
  abort: merging with a working directory ancestor has no effect
  [255]