Add lint for shellcheck, fix issues

Makefile

@@ -283,4 +283,13 @@ lint-staticcheck:
 lint-golangci-lint:
 	go run github.com/golangci/golangci-lint/cmd/golangci-lint@v1.59.0 run
 
-lint: lint-staticcheck lint-golangci-lint
+lint-shellcheck:
+	docker run \
+	    --rm \
+	    -v `pwd`:`pwd` \
+	    -w `pwd` \
+	    docker.io/koalaman/shellcheck-alpine:v0.9.0 \
+	        shellcheck \
+	        $$(git ls-files ':!:vendor' '*.sh')
+
+lint: lint-staticcheck lint-golangci-lint lint-shellcheck

_test_tools/git_askpass.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # Copyright 2019 The Kubernetes Authors.
 #
@@ -20,15 +20,15 @@ set -o errexit
 set -o nounset
 
 # Ask pass some ops, fail if it mismatched the magic password.
-if [ "$1" = "clone" -o "$1" = "ls-remote" -o "$1" = "fetch" ]; then
+if [[ "$1" == "clone" || "$1" == "ls-remote" || "$1" = "fetch" ]]; then
     # `git credential fill` requires the repo url match to consume the credentials stored by git-sync.
     # Askpass git only support repo started with "file://" which is used in test_e2e.sh.
     REPO=$(echo "$@" | grep -o "file://[^ ]*")
     OUTPUT=$(echo "url=${REPO}" | git credential fill)
     USERNAME=$(echo "${OUTPUT}" | grep "^username=.*")
     PASSWD=$(echo "${OUTPUT}" | grep "^password=.*")
     # Test case must match the magic username and password below.
-    if [ "${USERNAME}" != "username=my-username" -o "${PASSWD}" != "password=my-password" ]; then
+    if [[ "${USERNAME}" != "username=my-username" || "${PASSWD}" != "password=my-password" ]]; then
         echo "invalid test username/password pair: ${USERNAME}:${PASSWD}"
         exit 1
     fi

_test_tools/ncsvr/ncsvr.sh

@@ -14,17 +14,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
-if [ -z "$1" -o -z "$2" ]; then
+if [ -z "$1" ] || [ -z "$2" ]; then
     echo "usage: $0 <port> <shell-command>"
     exit 1
 fi
 
-F="/tmp/fifo.$RANDOM"
-
+# This construction allows the passed-in command ($2) to optionally read from
+# the client before responding (e.g. an HTTP request).
+CMD_TO_NC=$(mktemp -u)
+NC_TO_CMD=$(mktemp -u)
+mkfifo "$CMD_TO_NC" "$NC_TO_CMD"
 while true; do
-    rm -f "$F"
-    mkfifo "$F"
-    cat "$F" | sh -c "$2" 2>&1 | nc -l -p "$1" -N -w1 > "$F"
+    sh -c "$2" > "$CMD_TO_NC" 2>&1 < "$NC_TO_CMD" &
+    nc -l -p "$1" -N -w1 < "$CMD_TO_NC" > "$NC_TO_CMD"
     date >> /var/log/hits
 done