Use base64 strings for chart repo certs [#74]

This should be a more flexible option since certificates aren't likely
to be part of the actual workspace and may be environment-dependent. It
also mirrors the kube_certificate, which is nice.

internal/run/repocerts.go

@@ -0,0 +1,77 @@
+package run
+
+import (
+	"encoding/base64"
+	"fmt"
+	"github.com/pelotech/drone-helm3/internal/env"
+	"io/ioutil"
+)
+
+type repoCerts struct {
+	*config
+	cert           string
+	certFilename   string
+	caCert         string
+	caCertFilename string
+}
+
+func newRepoCerts(cfg env.Config) *repoCerts {
+	return &repoCerts{
+		config: newConfig(cfg),
+		cert:   cfg.RepoCertificate,
+		caCert: cfg.RepoCACertificate,
+	}
+}
+
+func (rc *repoCerts) write() error {
+	if rc.cert != "" {
+		file, err := ioutil.TempFile("", "repo********.cert")
+		defer file.Close()
+		if err != nil {
+			return fmt.Errorf("failed to create certificate file: %w", err)
+		}
+		rc.certFilename = file.Name()
+		rawCert, err := base64.StdEncoding.DecodeString(rc.cert)
+		if err != nil {
+			return fmt.Errorf("failed to base64-decode certificate string: %w", err)
+		}
+		if rc.debug {
+			fmt.Fprintf(rc.stderr, "writing repo certificate to %s\n", rc.certFilename)
+		}
+		if _, err := file.Write(rawCert); err != nil {
+			return fmt.Errorf("failed to write certificate file: %w", err)
+		}
+	}
+
+	if rc.caCert != "" {
+		file, err := ioutil.TempFile("", "repo********.ca.cert")
+		defer file.Close()
+		if err != nil {
+			return fmt.Errorf("failed to create CA certificate file: %w", err)
+		}
+		rc.caCertFilename = file.Name()
+		rawCert, err := base64.StdEncoding.DecodeString(rc.caCert)
+		if err != nil {
+			return fmt.Errorf("failed to base64-decode CA certificate string: %w", err)
+		}
+		if rc.debug {
+			fmt.Fprintf(rc.stderr, "writing repo ca certificate to %s\n", rc.caCertFilename)
+		}
+		if _, err := file.Write(rawCert); err != nil {
+			return fmt.Errorf("failed to write CA certificate file: %w", err)
+		}
+	}
+	return nil
+}
+
+func (rc *repoCerts) flags() []string {
+	flags := make([]string, 0)
+	if rc.certFilename != "" {
+		flags = append(flags, "--cert-file", rc.certFilename)
+	}
+	if rc.caCertFilename != "" {
+		flags = append(flags, "--ca-file", rc.caCertFilename)
+	}
+
+	return flags
+}