tests/test-issue612.t

lfs: infer the blob store URL from an explicit push dest or default-push

Unlike pull, the blobs are uploaded within the exchange.push() window, so simply
wrap it and swap in a properly configured remote store.  The '_subtoppath' field
shouldn't be available during this window, but give the passed path priority for
clarity.

At one point I hit an AttributeError in one of the convert tests when trying to
save the original remote blobstore when the swap was run unconditionally.  I
wrapped it in a util.safehasattr(), but then today I wasn't able to reproduce
it.  But now the whole thing is tucked under the requirement guard because
without the requirement, there are no blobs in the repo, even if the extension
is loaded.

https://bz.mercurial-scm.org/612

  $ hg init
  $ mkdir src
  $ echo a > src/a.c
  $ hg ci -Ama
  adding src/a.c

  $ hg mv src source
  moving src/a.c to source/a.c

  $ hg ci -Ammove

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

  $ echo new > src/a.c
  $ echo compiled > src/a.o
  $ hg ci -mupdate
  created new head

  $ hg status
  ? src/a.o

  $ hg merge
  merging src/a.c and source/a.c to source/a.c
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  M source/a.c
  R src/a.c
  ? src/a.o