tests/test-issue1877.t

stream-clone: add a explicit test for format change during stream clone

They are different kind of requirements, the one which impact the data storage
and are relevant to the files being streamed and the one which does not. For
example some requirements are only relevant to the working copy, like sparse, or
dirstate-v2.

Since they are irrelevant to the content being streamed, they do not prevent the
receiving side to use streaming clone and mercurial skip adverting them over
the wire and, ideally, within the bundle.

In addition, this let the client decide to use whichever format it desire for
the part that does not affect the store itself. So the configuration related to
these format are used as normal when doing a streaming clone.

In practice, the feature was not really tested and is badly broken with bundle-2,
since the requirements are not filtered out from the stream bundle.

So we start with adding simple tests as a good base before the fix and adjust
the feature.

Differential Revision: https://phab.mercurial-scm.org/D12029

https://bz.mercurial-scm.org/1877

  $ hg init a
  $ cd a
  $ echo a > a
  $ hg add a
  $ hg ci -m 'a'
  $ echo b > a
  $ hg ci -m'b'
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg book main
  $ hg book
   * main                      0:cb9a9f314b8b
  $ echo c > c
  $ hg add c
  $ hg ci -m'c'
  created new head
  $ hg book
   * main                      2:d36c0562f908
  $ hg heads
  changeset:   2:d36c0562f908
  bookmark:    main
  tag:         tip
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
  changeset:   1:1e6c11564562
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg up 1e6c11564562
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark main)
  $ hg merge main
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg book
     main                      2:d36c0562f908
  $ hg ci -m'merge'
  $ hg book
     main                      2:d36c0562f908

  $ cd ..