hack: reuse already installed golangci-lint

When a specific version of golangci-lint is already available in $PATH,
use it instead of installing one locally.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

hack/golangci-lint.sh

@@ -10,6 +10,9 @@ set -e
 
 declare -a EXTRA_TAGS
 
+# Prefer the one from $PATH, if available.
+BIN="$(command -v golangci-lint || echo ./bin/golangci-lint)"
+
 echo "Linting for GOOS=$GOOS"
 case "$GOOS" in
   windows|darwin)
@@ -31,6 +34,6 @@ for EXTRA in "" "${EXTRA_TAGS[@]}"; do
   # the command-line to focus or debug a single, specific linting category.
   (
     set -x
-    ./bin/golangci-lint run --build-tags="${TAGS}${EXTRA}" "$@"
+    "$BIN" run --build-tags="${TAGS}${EXTRA}" "$@"
   )
 done

hack/install_golangci.sh

@@ -10,6 +10,10 @@ die() { echo "${1:-No error message given} (from $(basename "$0"))"; exit 1; }
 # Strip the leading v, if found.
 VERSION=${VERSION#v}
 
+# Local installation path.
+BINDIR="./bin"
+LBIN="$BINDIR/golangci-lint"
+
 function install() {
     local retry=$1
 
@@ -22,10 +26,20 @@ function install() {
     curl -sSfL --retry 5 https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b $BINDIR "v$VERSION"
 }
 
-BINDIR="./bin"
-BIN="$BINDIR/golangci-lint"
-if [ -x "$BIN" ] && $BIN --version | grep "$VERSION"; then
+# Check if it's already installed globally.
+BIN=$(command -v golangci-lint)
+if [ -n "$BIN" ] && $BIN --version | grep "$VERSION"; then
     echo "Using existing $BIN"
+    # Remove the locally installed one, as it is:
+    #  - no longer needed;
+    #  - might be old/wrong version.
+    rm -f $LBIN
+    exit 0
+fi
+
+# Check the locally installed one.
+if [ -x "$LBIN" ] && $LBIN --version | grep "$VERSION"; then
+    echo "Using existing local $LBIN"
     exit 0
 fi