Googletest export

Clarify use of IsTrue and IsFalse matchers.

These matchers are subtle and confusing: what are they for?
The docs in the code are clear, but not very accessible.
googletest/googlemock/include/gmock/gmock-more-matchers.h

PiperOrigin-RevId: 283393275

googlemock/docs/cheat_sheet.md

@@ -278,6 +278,12 @@ copy constructor, try wrap it in `ByRef()`, e.g.
 `Eq(ByRef(non_copyable_value))`. If you do that, make sure `non_copyable_value`
 is not changed afterwards, or the meaning of your matcher will be changed.
 
+`IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types
+that can be explicitly converted to Boolean, but are not implicitly converted to
+Boolean. In other cases, you can use the basic
+[`EXPECT_TRUE` and `EXPECT_FALSE`](../../googletest/docs/primer#basic-assertions)
+assertions.
+
 #### Floating-Point Matchers {#FpMatchers}
 
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