tests/test-merge5.t

test-chg: use a different log to avoid flakyness

The test was deleting the log file to start anew. However a trailing working
process might still be alive at this time, and recreate the very same log on
exit.

We see the trace of such worker in the expected content of server.log (see the
trace modified by this patch). This is flaky because we don't know *when* the
worker will write to the file and there is a race with the `hg init cached`
command.

A much simpler and reliable way to start anew without having such race is… to
write to a different log file. No reuse → no conflict, no conflict → no race, no
race → no flakiness.

  $ hg init repo
  $ cd repo
  $ echo This is file a1 > a
  $ echo This is file b1 > b
  $ hg add a b
  $ hg commit -m "commit #0"
  $ echo This is file b22 > b
  $ hg commit -m "comment #1"
  $ hg update 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm b
  $ hg commit -A -m "comment #2"
  removing b
  created new head
  $ hg update 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm b
  $ hg update -c 2
  abort: uncommitted changes
  [20]
  $ hg revert b
  $ hg update -c 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mv a c

Should abort:

  $ hg update 1
  abort: uncommitted changes
  (commit or update --clean to discard changes)
  [255]
  $ mv c a

Should succeed:

  $ hg update 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved