Show flag name instead of True/False with Boolean flags

[ovezovs]

Fixes #1538

[ovezovs]

@davidism, I have one major question regarding this fix: Should we show the flag names only for boolean flags or any? For example, test_global_show_default expects default on the help flag line to be false. For now, I did a workaround to not display the default flag name when it is help. I am not sure if that's a bad thing.

[juped]

I recommend splitting the history into maybe two commits (one something like "Display flag name instead of True/False for default in help" and one "Add test [...]"), or maybe just one

[davidism]

Unless the test is particularly complex, I usually just roll it into the code commit. Same for multiple code and cleanup commits into a single commit.

[davidism]

Updated the implementation so that it checks that the boolean flag actually has separate flags for True and False. It selects them from self.opts and self.secondary_opts instead of rv, since rv will have , joined alternative names together. That would cause the following:

@click.option("--cache/--no-cache", "--c/--nc", show_default=True)

[default: no-cache, --nc]

Now it outputs only no-cache.

Updated the test to check when default is True and False, and added a second test for when there's only one name.

[ovezovs]

Updated the implementation so that it checks that the boolean flag actually has separate flags for True and False. It selects them from self.opts and self.secondary_opts instead of rv, since rv will have , joined alternative names together. That would cause the following:

@click.option("--cache/--no-cache", "--c/--nc", show_default=True)

[default: no-cache, --nc]

Now it outputs only no-cache.

Updated the test to check when default is True and False, and added a second test for when there's only one name.

Thank you so much for the feedback!