Review comments #1.

vet.sh

@@ -3,9 +3,8 @@
 set -ex  # Exit on error; debugging enabled.
 set -o pipefail  # Fail a pipe if any sub-command fails.
 
-# negate_and_run makes sure that no output is seen when executing the command
-# passed to it as args.
-negate_and_run() {
+# not makes sure the command passed to it does not exit with a return code of 0.
+not() {
   # This is required instead of the earlier (! $COMMAND) because subshells and
   # pipefail don't work the same on Darwin as in Linux.
   ! eval "$*"
@@ -17,7 +16,7 @@ die() {
 }
 
 fail_on_output() {
-  tee /dev/stderr | negate_and_run read
+  tee /dev/stderr | not read
 }
 
 # Check to make sure it's safe to modify the user's git repo.
@@ -73,21 +72,21 @@ elif [[ "$#" -ne 0 ]]; then
 fi
 
 # - Ensure all source files contain a copyright message.
-negate_and_run 'git grep -L "\(Copyright [0-9]\{4,\} gRPC authors\)\|DO NOT EDIT" -- *.go'
+not 'git grep -L "\(Copyright [0-9]\{4,\} gRPC authors\)\|DO NOT EDIT" -- *.go'
 
 # - Make sure all tests in grpc and grpc/test use leakcheck via Teardown.
-negate_and_run 'grep "func Test[^(]" *_test.go'
-negate_and_run 'grep "func Test[^(]" test/*.go'
+not 'grep "func Test[^(]" *_test.go'
+not 'grep "func Test[^(]" test/*.go'
 
 # - Do not import x/net/context.
-negate_and_run 'git grep -l "x/net/context" -- *.go'
+not 'git grep -l "x/net/context" -- *.go'
 
 # - Do not import math/rand for real library code.  Use internal/grpcrand for
 #   thread safety.
-git grep -l '"math/rand"' -- "*.go" 2>&1 | negate_and_run 'grep -v "^examples\|^stress\|grpcrand\|^benchmark\|wrr_test"'
+git grep -l '"math/rand"' -- "*.go" 2>&1 | not 'grep -v "^examples\|^stress\|grpcrand\|^benchmark\|wrr_test"'
 
 # - Ensure all ptypes proto packages are renamed when importing.
-negate_and_run 'git grep "\(import \|^\s*\)\"github.com/golang/protobuf/ptypes/" -- "*.go"'
+not 'git grep "\(import \|^\s*\)\"github.com/golang/protobuf/ptypes/" -- "*.go"'
 
 # - Check imports that are illegal in appengine (until Go 1.11).
 # TODO: Remove when we drop Go 1.10 support