Add GTEST_QUIET option

[calumr]

Only prints failures and a total pass count. This is useful for CI logs, which are more useful if they just have the failures instead of 100s or 1000s of lines of "PASSED" and the one failure buried in the middle.

Fixes #358, which was closed but seems to have a few fans...

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[calumr]

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[vslashg]

We are open to this change, but have a couple of suggestions.

First, the name "quiet" seems to suggest that Google Test won't emit any output (reporting results by exit code only.) Maybe a different word is more appropriate, perhaps "brief"?

Second, adding a bunch of early exits to PrettyUnitTestResultPrinter feels slightly off. We think it could work out cleaner to have a second implementation of TestEventListener for brief output, and install the appropriate listener based on the flag setting.

[vslashg]

"T to show" appears to be a typo.

[calumr]

Thanks, fixed in the last push.

[calumr]

You were totally right about adding another TestEventListener - it's much cleaner this way. There is some code duplication though, I can understand if you want me to clean that up.

I went a little further and removed the PrintFailedTests calls too, they are just duplicating the information printed from OnTestEnd.

[lishuai87]

ctest has option --output-on-failure, why gtest not support it?

https://cmake.org/cmake/help/latest/manual/ctest.1.html#options