view tests/test-revlog-ancestry.py.out @ 26454:62c5e937f477

pager: recreate stdout to make it line-buffered

We want to see partial command results as soon as possible. But the buffering
mode of stdout (= pager's stdin) was set to fully-buffered because it isn't
associated with a tty. So, this patch recreates new stdout object to force its
buffering mode.

Because two file objects are associated with the same stdout fd and their
destructors will call close(), one of them must be closed carefully. Python
expects that the stdout fd never be closed even after sys.stdout.close() [1],
but newstdout has no such hack. So this patch calls newstdout.close()
immediately before duplicating the original stdout fd to sys.stdout.

  operation              sys.stdout  newstdout  fd
  ---------------------  ----------  ---------  --------
  newstdout.close()      open        closed     closed
  os.dup2(stdoutfd, ..)  open        closed     open
  del sys.stdout         closed      closed     open [1]

 [1]: https://hg.python.org/cpython/file/v2.7.10/Python/sysmodule.c#l1391

Ancestors of 5
4 2 0 
Ancestors of 6 and 5
3 4 2 1 0 
Ancestors of 5 and 4
4 2 0 
Ancestors of 7, stop at 6
6 
Ancestors of 7, including revs
7 6 5 3 4 2 1 0 
Ancestors of 7, 5 and 3, including revs
7 5 3 6 4 2 1 0 

Descendants of 5
7 8 
Descendants of 5 and 3
6 7 8 
Descendants of 5 and 4
5 7 8