Update README.rst

[Jylpah]

I propose adding clarification of the abbreviations in the coverage report. These are not mentioned anywhere in the documentation and there is even a StackOverflow question about those.

===== Addition to section "Usage" under the report ========

Where,

• Stmts refers to the number of statements in your code.
• Miss refers to the number of statements that have not been run.
• Cover is test coverage, or (Stmts - Miss) / (Stmts) * 100.

===========================================

I can understand these are "obvious" for the experienced programmers, but maybe not for someone taking a code coverage tool into use for the first time.

I understand you want to keep the documentation short and to the point (it is).

[nedbat]

Another option: add information like this to the coverage.py docs, with a clear indication from here that much of the pytest-cov behavior is from coverage.py.

[elrandira]

additionally, I have reports with Missing, Branch and BrPart columns.

As well some explanation on the coverage would be useful. I have notation like these in the Missing column:

• 67: make sense
• 128->130: make sense
• 171->168: ???
• 189->exit: ???