Add option/config to collapse file/module/line data for warnings

[goodspark]

Python 3.8.1
pytest 5.3.4
Ubuntu 18.04

pip list
Package        Version
-------------- -------
attrs          19.3.0 
more-itertools 8.1.0  
packaging      20.1   
pip            20.0.2 
pluggy         0.13.1 
py             1.8.1  
pyparsing      2.4.6  
pytest         5.3.4  
setuptools     45.1.0 
six            1.14.0 
wcwidth        0.1.8  
wheel          0.34.1 

test_it.py

import pytest
import warnings

@pytest.mark.parametrize("a", sorted(range(3)))
def test_1(a):
    warnings.warn("deprecated", DeprecationWarning)

pytest .
===================== test session starts ======================
platform linux -- Python 3.8.1, pytest-5.3.4, py-1.8.1, pluggy-0.13.1
rootdir: /home/sam/tmp/py38, inifile: setup.cfg
collected 3 items                                              

test_it.py ...                                           [100%]

======================= warnings summary =======================
test_it.py::test_1[0]
test_it.py::test_1[1]
test_it.py::test_1[2]
  /home/sam/tmp/py38/test_it.py:6: DeprecationWarning: deprecated
    warnings.warn("deprecated", DeprecationWarning)

-- Docs: https://docs.pytest.org/en/latest/warnings.html
================ 3 passed, 3 warnings in 0.01s =================

I'd like a way to hide/collapse/combine all the file/module/line data that gets printed out in the warnings summary. For larger projects with spaghetti code, it's quite possible this print out ends up being hundreds of lines long.

The same happens when I try to use the "once" action for filter warnings. Which kind of makes sense. That warning is still only being shown 'once'.

[blueyed]

Makes sense.
Note that there is some collapsing being done for "SKIPPED", but it could be improved in general also (e.g. with regard to providing an option to collapse / collapsing similar skips via/from different source lines).
So this should likely be looked at / refactored when doing it for warnings then.

[nicoddemus]

Perhaps makes sense to collapse automatically with the default verbosity, and keep the existing display with -v or greater?