GODT-1523: Reduce unnecessary shell executions. Inspired by @kortschak.

- check opened file descriptors
- detection of darwin version
- detection of apple interface color theme
- test for update sync (copy files)
- replace exec with execabs

internal/frontend/clientconfig/config_applemail.go

@@ -23,7 +23,6 @@ package clientconfig
 import (
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -33,6 +32,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v2/internal/config/useragent"
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/types"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/mobileconfig"
+	"golang.org/x/sys/execabs"
 )
 
 const (
@@ -56,10 +56,10 @@ func (c *appleMail) Configure(imapPort, smtpPort int, imapSSL, smtpSSL bool, use
 	}
 
 	if useragent.IsBigSurOrNewer() {
-		return exec.Command("open", bigSurPreferncesPane, confPath).Run() //nolint:gosec G204: open command is safe, mobileconfig is generated by us
+		return execabs.Command("open", bigSurPreferncesPane, confPath).Run() //nolint:gosec G204: open command is safe, mobileconfig is generated by us
 	}
 
-	return exec.Command("open", confPath).Run() //nolint:gosec G204: open command is safe, mobileconfig is generated by us
+	return execabs.Command("open", confPath).Run() //nolint:gosec G204: open command is safe, mobileconfig is generated by us
 }
 
 func prepareMobileConfig(imapPort, smtpPort int, imapSSL, smtpSSL bool, user types.User, address string) *mobileconfig.Config {

internal/frontend/theme/detect_darwin.go

@@ -21,14 +21,34 @@
 package theme
 
 import (
-	"os/exec"
-	"strings"
+	"os"
+	"path/filepath"
+
+	"howett.net/plist"
 )
 
 func detectSystemTheme() Theme {
-	out, err := exec.Command("defaults", "read", "-g", "AppleInterfaceStyle").Output() //nolint:gosec
-	if err == nil && strings.TrimSpace(string(out)) == "Dark" {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return Light
+	}
+
+	path := filepath.Join(home, "/Library/Preferences/.GlobalPreferences.plist")
+	prefFile, err := os.Open(path)
+	if err != nil {
+		return Light
+	}
+	defer prefFile.Close()
+
+	var data struct {
+		AppleInterfaceStyle string `plist:AppleInterfaceStyle`
+	}
+
+	dec := plist.NewDecoder(prefFile)
+	err = dec.Decode(&data)
+	if err == nil && data.AppleInterfaceStyle == "Dark" {
 		return Dark
 	}
+
 	return Light
 }