tests/test-rename-after-merge.t

debugcommands: introduce actions to perform deterministic reads

"readavailable" is useful as a debugging device to see what data is
available on a pipe. But the mechanism isn't deterministic because
what's available on a pipe is highly conditional on timing, system
load, OS behavior, etc. This makes it not suitable for tests.

We introduce "ereadline," "read," and "eread" for performing
deterministic I/O operations (at least on blocking file descriptors).

We stop short of converting existing consumers of "readavailable"
in tests because we're working out race conditions and deadlocks
on Windows. But the goal is to eventually move tests away from
"readavailable" to these new APIs.

Differential Revision: https://phab.mercurial-scm.org/D2720

Issue746: renaming files brought by the second parent of a merge was
broken.

Create source repository:

  $ hg init t
  $ cd t
  $ echo a > a
  $ hg ci -Am a
  adding a
  $ cd ..

Fork source repository:

  $ hg clone t t2
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd t2
  $ echo b > b
  $ hg ci -Am b
  adding b

Update source repository:

  $ cd ../t
  $ echo a >> a
  $ hg ci -m a2

Merge repositories:

  $ hg pull ../t2
  pulling from ../t2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets d2ae7f538514
  (run 'hg heads' to see heads, 'hg merge' to merge)

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

  $ hg st
  M b

Rename b as c:

  $ hg mv b c
  $ hg st
  A c
  R b

Rename back c as b:

  $ hg mv c b
  $ hg st
  M b

  $ cd ..

Issue 1476: renaming a first parent file into another first parent
file while none of them belong to the second parent was broken

  $ hg init repo1476
  $ cd repo1476
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ echo b1 > b1
  $ echo b2 > b2
  $ hg ci -Am changea
  adding b1
  adding b2
  $ hg up -C 0
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo c1 > c1
  $ echo c2 > c2
  $ hg ci -Am addcandd
  adding c1
  adding c2
  created new head

Merge heads:

  $ hg merge
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg mv -Af c1 c2

Commit issue 1476:

  $ hg ci -m merge

  $ hg log -r tip -C -v | grep copies
  copies:      c2 (c1)

  $ hg rollback
  repository tip rolled back to revision 2 (undo commit)
  working directory now based on revisions 2 and 1

  $ hg up -C .
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved

Merge heads again:

  $ hg merge
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg mv -Af b1 b2

Commit issue 1476 with a rename on the other side:

  $ hg ci -m merge

  $ hg log -r tip -C -v | grep copies
  copies:      b2 (b1)

  $ cd ..