Generator command dumps the whole output at once when piped

[neithere]

Example program

#!/usr/bin/python
from time import sleep

import argh

def main():
    for i in range(3):
        sleep(1)
        yield f'line {i}'

argh.dispatch_command(main)

Case A:

$ ./app.py
0
1
2

The output is printed line by line with pauses.

Case B:

$ ./app.py | tail -f
0
1
2

The output is the same but it's printed all at once after 3 seconds.

Another way to repro case B:

# in terminal 1:
$ touch app.log && tail -f app.log

# in terminal 2:
$ ./app.py > app.log

[neithere]

Actually tail is not a good example; better use grep or cat for testing.

Fixed in #202 — added a new argument always_flush to dispatch().