Junio C Hamano <gitster@xxxxxxxxx> writes:
> Erik Faye-Lund <kusmabite@xxxxxxxxx> writes:
>
>>> + /* Use editor if stdin and stdout are the same and is a tty */
>>> + return (!fstat(0, &st_stdin) &&
>>> + !fstat(1, &st_stdout) &&
>>> + isatty(0) &&
>>> + st_stdin.st_dev == st_stdout.st_dev &&
>>> + st_stdin.st_ino == st_stdout.st_ino &&
>>> + st_stdin.st_mode == st_stdout.st_mode);
>>
>> I just stumbled over this code, and I got a bit worried; the
>> stat-implementation we use on Windows sets st_ino to 0, so
>> "st_stdin.st_ino == st_stdout.st_ino" will always evaluate to true.
>>
>> Perhaps we should add a check for isatty(1) here as well? ...
>> Or is there something I'm missing here?
>
> No, the intention was ...
s/No,/No, you are not missing anything./;
I'll queue it with this explanation:
merge: do not trust fstat(2) too much when checking interactiveness
The heuristic used by "git merge" to decide if it automatically gives an
editor upon clean automerge is to see if the standard input and the
standard output is the same device and is a tty, we are in an interactive
session. "The same device" test was done by comparing fstat(2) result on
the two file descriptors (and they must match), and we asked isatty() only
for the standard input (we insist that they are the same device and there
is no point asking tty-ness of the standard output).
The stat(2) emulation on Windows port however does not give a usable value
in st_ino field, so even if the standard output is connected to something
different from the standard input, "The same device" test may incorrectly
return true. To accomodate it, add another isatty() check for the standard
output stream as well.
Reported-by: Erik Faye-Lund <kusmabite@xxxxxxxxx>
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
Thanks.
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