4 files changed, 158 insertions, 3 deletions
diff --git a/internal/cli/description_sync.go b/internal/cli/description_sync.go
index 4904b56..317bcdf 100644
--- a/internal/cli/description_sync.go
+++ b/internal/cli/description_sync.go
@@ -2,6 +2,10 @@ package cli
 
 import (
 	"fmt"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
 	"strings"
 
 	"codeberg.org/snonux/gitsyncer/internal/codeberg"
@@ -105,8 +109,75 @@ func syncRepoDescriptions(cfg *config.Config, dryRun bool, repoName, knownCBDesc
 		}
 	}
 
+	syncBackupDescriptions(cfg, dryRun, repoName, canonical)
+
 	// Update cache
 	if cache != nil {
 		cache[repoName] = canonical
 	}
 }
+
+func syncBackupDescriptions(cfg *config.Config, dryRun bool, repoName, canonical string) {
+	if cfg == nil || canonical == "" {
+		return
+	}
+
+	for i := range cfg.Organizations {
+		org := &cfg.Organizations[i]
+		if !org.BackupLocation {
+			continue
+		}
+
+		supported, err := syncBackupDescription(org, repoName, canonical, dryRun)
+		if err != nil {
+			fmt.Printf("  Warning: Failed to update backup description on %s: %v\n", org.Host, err)
+			continue
+		}
+		if supported && !dryRun {
+			fmt.Printf("  Updated backup description for %s on %s\n", repoName, org.Host)
+		}
+	}
+}
+
+func syncBackupDescription(org *config.Organization, repoName, description string, dryRun bool) (bool, error) {
+	if org == nil || !org.BackupLocation {
+		return false, nil
+	}
+
+	description = strings.TrimSpace(description)
+	if description == "" {
+		return false, nil
+	}
+
+	if strings.HasPrefix(org.Host, "file://") {
+		descriptionPath := filepath.Join(strings.TrimPrefix(org.Host, "file://"), repoName+".git", "description")
+		if dryRun {
+			fmt.Printf("  [DRY RUN] Would update backup description for %s on %s -> %q\n", repoName, org.Host, description)
+			return true, nil
+		}
+		return true, os.WriteFile(descriptionPath, []byte(description+"\n"), 0644)
+	}
+
+	if strings.TrimSpace(org.DescriptionSyncHost) == "" || strings.TrimSpace(org.DescriptionSyncRoot) == "" {
+		return false, nil
+	}
+
+	descriptionPath := path.Join(org.DescriptionSyncRoot, repoName+".git", "description")
+	if dryRun {
+		fmt.Printf("  [DRY RUN] Would update backup description for %s on %s -> %q\n", repoName, org.Host, description)
+		return true, nil
+	}
+
+	cmd := exec.Command("ssh", org.DescriptionSyncHost, fmt.Sprintf("cat > %s", shellSingleQuote(descriptionPath)))
+	cmd.Stdin = strings.NewReader(description + "\n")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return true, fmt.Errorf("ssh write failed: %w\n%s", err, strings.TrimSpace(string(output)))
+	}
+
+	return true, nil
+}
+
+func shellSingleQuote(value string) string {
+	return "'" + strings.ReplaceAll(value, "'", `'\''`) + "'"
+}
diff --git a/internal/cli/description_sync_test.go b/internal/cli/description_sync_test.go
new file mode 100644
index 0000000..8f92349
--- /dev/null
+++ b/internal/cli/description_sync_test.go
@@ -0,0 +1,57 @@
+package cli
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"codeberg.org/snonux/gitsyncer/internal/config"
+)
+
+func TestSyncBackupDescription_FileURLWritesDescription(t *testing.T) {
+	t.Parallel()
+
+	rootDir := t.TempDir()
+	repoDir := filepath.Join(rootDir, "sample.git")
+	if err := os.MkdirAll(repoDir, 0755); err != nil {
+		t.Fatalf("mkdir repo dir: %v", err)
+	}
+
+	org := &config.Organization{
+		Host:           "file://" + rootDir,
+		BackupLocation: true,
+	}
+
+	supported, err := syncBackupDescription(org, "sample", "Sample description", false)
+	if err != nil {
+		t.Fatalf("syncBackupDescription() error = %v", err)
+	}
+	if !supported {
+		t.Fatal("expected file backup description sync to be supported")
+	}
+
+	content, err := os.ReadFile(filepath.Join(repoDir, "description"))
+	if err != nil {
+		t.Fatalf("read description: %v", err)
+	}
+	if string(content) != "Sample description\n" {
+		t.Fatalf("description = %q, want %q", string(content), "Sample description\n")
+	}
+}
+
+func TestSyncBackupDescription_SSHWithoutDescriptionSyncConfigIsUnsupported(t *testing.T) {
+	t.Parallel()
+
+	org := &config.Organization{
+		Host:           "ssh://git@example.com/repos",
+		BackupLocation: true,
+	}
+
+	supported, err := syncBackupDescription(org, "sample", "Sample description", false)
+	if err != nil {
+		t.Fatalf("syncBackupDescription() error = %v", err)
+	}
+	if supported {
+		t.Fatal("expected SSH backup description sync without config to be unsupported")
+	}
+}
diff --git a/internal/cli/sync_handlers.go b/internal/cli/sync_handlers.go
index 6a96b92..e791b45 100644
--- a/internal/cli/sync_handlers.go
+++ b/internal/cli/sync_handlers.go
@@ -12,6 +12,14 @@ import (
 	"codeberg.org/snonux/gitsyncer/internal/sync"
 )
 
+func shouldEnableBackupSync(flags *Flags) bool {
+	if flags == nil {
+		return false
+	}
+
+	return flags.Backup || flags.FullSync
+}
+
 // HandleSync handles syncing a single repository
 func HandleSync(cfg *config.Config, flags *Flags) int {
 	stateManager, syncState, err := loadSyncState(flags.WorkDir)
@@ -50,7 +58,7 @@ func HandleSync(cfg *config.Config, flags *Flags) int {
 	}
 
 	syncer := sync.New(cfg, flags.WorkDir)
-	syncer.SetBackupEnabled(flags.Backup)
+	syncer.SetBackupEnabled(shouldEnableBackupSync(flags))
 	if err := syncer.SyncRepository(flags.SyncRepo); err != nil {
 		fmt.Printf("ERROR: Sync failed: %v\n", err)
 		return 1
@@ -107,7 +115,7 @@ func HandleSyncAll(cfg *config.Config, flags *Flags) int {
 	}
 
 	syncer := sync.New(cfg, flags.WorkDir)
-	syncer.SetBackupEnabled(flags.Backup)
+	syncer.SetBackupEnabled(shouldEnableBackupSync(flags))
 	successCount := 0
 	// Load descriptions cache
 	descCache := loadDescriptionCache(flags.WorkDir)
@@ -421,7 +429,7 @@ func newSyncExecution(cfg *config.Config, flags *Flags) *syncExecution {
 		descCache: loadDescriptionCache(flags.WorkDir),
 		syncer:    sync.New(cfg, flags.WorkDir),
 	}
-	execution.syncer.SetBackupEnabled(flags.Backup)
+	execution.syncer.SetBackupEnabled(shouldEnableBackupSync(flags))
 
 	manager, st, err := loadSyncState(flags.WorkDir)
 	if err != nil {
diff --git a/internal/cli/sync_handlers_test.go b/internal/cli/sync_handlers_test.go
new file mode 100644
index 0000000..2eaad67
--- /dev/null
+++ b/internal/cli/sync_handlers_test.go
@@ -0,0 +1,19 @@
+package cli
+
+import "testing"
+
+func TestShouldEnableBackupSync_FullSyncImplicitlyEnablesBackup(t *testing.T) {
+	t.Parallel()
+
+	if !shouldEnableBackupSync(&Flags{FullSync: true}) {
+		t.Fatal("expected full sync to enable backup sync implicitly")
+	}
+
+	if !shouldEnableBackupSync(&Flags{Backup: true}) {
+		t.Fatal("expected explicit --backup to enable backup sync")
+	}
+
+	if shouldEnableBackupSync(&Flags{}) {
+		t.Fatal("did not expect backup sync to be enabled by default")
+	}
+}