hack/install_golang.sh: revamp

1. Strip leading v from VERSION.

This will allow to simplify renovate rule at [1].

2. Fix git branch in the URL.

In golangci-lint v2 they've switched from master to main,
and it's not clear what will happen to master over time,
so let's just switch to main prophylactically.

3. Use -b option instead of undocumented hack.

Instead of relying on an undocumented feature of having BINDIR,
let's use -b option as recommended by the official docs at [2].

4. Avoid stuttering in the output.

Before:

	[kir@kir-tp1 podman]$ VERSION=2.0.2 ./hack/install_golangci.sh
	golangci-lint has version 2.0.2 built with go1.24.1 from 2b224c2c on 2025-03-25T21:36:18Z
	Using existing ./bin/golangci-lint has version 2.0.2 built with go1.24.1 from 2b224c2c on 2025-03-25T21:36:18Z

After:

	[kir@kir-tp1 podman]$ VERSION=2.0.2 ./hack/install_golangci.sh
	golangci-lint has version 2.0.2 built with go1.24.1 from 2b224c2c on 2025-03-25T21:36:18Z
	Using existing ./bin/golangci-lint

5. Fix shellcheck warnings.

6. Also retry when reinstalling.

The code logic to retry install for up to 5 times when installation
fails was introduced by commit dd8574022d ("CI: retry the golangci
install").

For some reason, the above commit only uses the logic when the binary is
not found. In a situation when the binary is found but is of the wrong
version, no retries are done.

Fix that.

7. Add -f option to curl.

As recommended by the official installation docs at [2].

[1]: 16f757f699/renovate/defaults.json5 (L106-L108)
[2]: https://golangci-lint.run/welcome/install/#binaries

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

hack/install_golangci.sh

@@ -3,10 +3,13 @@
 # This script is intended to be a convenience, to be called from the
 # Makefile `.install.golangci-lint` target.  Any other usage is not recommended.
 
-die() { echo "${1:-No error message given} (from $(basename $0))"; exit 1; }
+die() { echo "${1:-No error message given} (from $(basename "$0"))"; exit 1; }
 
 [ -n "$VERSION" ] || die "\$VERSION is empty or undefined"
 
+# Strip the leading v, if found.
+VERSION=${VERSION#v}
+
 function install() {
     local retry=$1
 
@@ -14,27 +17,20 @@ function install() {
     if [[ $retry -ne 0 ]]; then
         msg+=" - retry #$retry"
     fi
-    echo $msg
+    echo "$msg"
 
-    curl -sSL --retry 5 https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s v$VERSION
+    curl -sSfL --retry 5 https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b $BINDIR "v$VERSION"
 }
 
-# Undocumented behavior: golangci-lint installer requires $BINDIR in env,
-# will default to ./bin but we can't rely on that.
-export BINDIR="./bin"
+BINDIR="./bin"
 BIN="$BINDIR/golangci-lint"
-if [ ! -x "$BIN" ]; then
-    # This flakes much too frequently with "crit unable to find v1.51.1"
-    for retry in $(seq 0 5); do
-	install $retry && exit 0
-        sleep 5
-    done
-else
-    # Prints its own file name as part of --version output
-    $BIN --version | grep "$VERSION"
-    if [ $? -eq 0 ]; then
-        echo "Using existing $BINDIR/$($BIN --version)"
-    else
-        install
-    fi
+if [ -x "$BIN" ] && $BIN --version | grep "$VERSION"; then
+    echo "Using existing $BIN"
+    exit 0
 fi
+
+# This flakes much too frequently with "crit unable to find v1.51.1"
+for retry in $(seq 0 5); do
+    install "$retry" && exit 0
+    sleep 5
+done