staticcheck (#313)

* CI: use staticcheck for linting

This commit switches the linter for Go code from golint to staticcheck.
Golint has been deprecated since last year and staticcheck is a
recommended replacement.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* revendor

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* cmd,pkg: fix lint warnings

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

vendor/honnef.co/go/tools/lintcmd/config.go

@@ -0,0 +1,105 @@
+package lintcmd
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"unicode"
+)
+
+type parseBuildConfigError struct {
+	line int
+	err  error
+}
+
+func (err parseBuildConfigError) Error() string { return err.err.Error() }
+
+func parseBuildConfigs(r io.Reader) ([]BuildConfig, error) {
+	var builds []BuildConfig
+	br := bufio.NewReader(r)
+	i := 0
+	for {
+		line, err := br.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				break
+			} else {
+				return nil, err
+			}
+		}
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		name, envs, flags, err := parseBuildConfig(line)
+		if err != nil {
+			return nil, parseBuildConfigError{line: i + 1, err: err}
+		}
+
+		bc := BuildConfig{
+			Name:  name,
+			Envs:  envs,
+			Flags: flags,
+		}
+		builds = append(builds, bc)
+
+		i++
+	}
+	return builds, nil
+}
+
+func parseBuildConfig(line string) (name string, envs []string, flags []string, err error) {
+	if line == "" {
+		return "", nil, nil, errors.New("couldn't parse empty build config")
+	}
+	if strings.Index(line, ":") == len(line)-1 {
+		name = line[:len(line)-1]
+	} else {
+		idx := strings.Index(line, ": ")
+		if idx == -1 {
+			return name, envs, flags, errors.New("missing build name")
+		}
+		name = line[:idx]
+
+		var buf []rune
+		var inQuote bool
+		args := &envs
+		for _, r := range strings.TrimSpace(line[idx+2:]) {
+			switch r {
+			case ' ':
+				if inQuote {
+					buf = append(buf, r)
+				} else if len(buf) != 0 {
+					if buf[0] == '-' {
+						args = &flags
+					}
+					*args = append(*args, string(buf))
+					buf = buf[:0]
+				}
+			case '"':
+				inQuote = !inQuote
+			default:
+				buf = append(buf, r)
+			}
+		}
+
+		if len(buf) > 0 {
+			if inQuote {
+				return "", nil, nil, errors.New("unterminated quoted string")
+			}
+			if buf[0] == '-' {
+				args = &flags
+			}
+			*args = append(*args, string(buf))
+		}
+	}
+
+	for _, r := range name {
+		if !(r == '_' || unicode.IsLetter(r) || unicode.IsNumber(r)) {
+			return "", nil, nil, fmt.Errorf("invalid build name %q", name)
+		}
+	}
+	return name, envs, flags, nil
+}