testing: clarify T.Name returns a distinct name of the running test

According to the discussion, it is clear that T.Name returns a
distinct name among all tests. However, there is no specification
of how sub-tests with the same specified test name are constructed.
This change only clarifies the uniqueness and the components of the
name without suggesting any explicit format of the returned name.

Fixes #46488

Change-Id: I6cebd419b69fb08d8646cb744a129548452042ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/337392
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Emmanuel Odeke <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: changkun

src/testing/testing.go

@@ -680,7 +680,11 @@ type T struct {
 
 func (c *common) private() {}
 
-// Name returns the name of the running test or benchmark.
+// Name returns the name of the running (sub-) test or benchmark.
+//
+// The name will include the name of the test along with the names of
+// any nested sub-tests. If two sibling sub-tests have the same name,
+// Name will append a suffix to guarantee the returned name is unique.
 func (c *common) Name() string {
 	return c.name
 }