Deduplicate step docker container volumes (#1571)

Try to fix #1495

It's very hard to reproduce it and only way to fix when it gets in this
state is woodpecker agent restart.

This anyway fixes problem if step mounts and
`WOODPECKER_BACKEND_DOCKER_VOLUMES` conflict

pipeline/backend/docker/docker.go

@@ -31,6 +31,7 @@ import (
 	"github.com/rs/zerolog/log"
 
 	backend "github.com/woodpecker-ci/woodpecker/pipeline/backend/types"
+	"github.com/woodpecker-ci/woodpecker/shared/utils"
 )
 
 type docker struct {
@@ -133,12 +134,11 @@ func (e *docker) Exec(ctx context.Context, step *backend.Step) error {
 	if step.Pull {
 		responseBody, perr := e.client.ImagePull(ctx, config.Image, pullopts)
 		if perr == nil {
-			defer responseBody.Close()
-
 			fd, isTerminal := term.GetFdInfo(os.Stdout)
 			if err := jsonmessage.DisplayJSONMessagesStream(responseBody, os.Stdout, fd, isTerminal, nil); err != nil {
 				log.Error().Err(err).Msg("DisplayJSONMessagesStream")
 			}
+			responseBody.Close()
 		}
 		// Fix "Show warning when fail to auth to docker registry"
 		// (https://web.archive.org/web/20201023145804/https://github.com/drone/drone/issues/1917)
@@ -148,7 +148,7 @@ func (e *docker) Exec(ctx context.Context, step *backend.Step) error {
 	}
 
 	// add default volumes to the host configuration
-	hostConfig.Binds = append(hostConfig.Binds, e.volumes...)
+	hostConfig.Binds = utils.DedupStrings(append(hostConfig.Binds, e.volumes...))
 
 	_, err := e.client.ContainerCreate(ctx, config, hostConfig, nil, nil, step.Name)
 	if client.IsErrNotFound(err) {
@@ -158,11 +158,11 @@ func (e *docker) Exec(ctx context.Context, step *backend.Step) error {
 		if perr != nil {
 			return perr
 		}
-		defer responseBody.Close()
 		fd, isTerminal := term.GetFdInfo(os.Stdout)
 		if err := jsonmessage.DisplayJSONMessagesStream(responseBody, os.Stdout, fd, isTerminal, nil); err != nil {
 			log.Error().Err(err).Msg("DisplayJSONMessagesStream")
 		}
+		responseBody.Close()
 
 		_, err = e.client.ContainerCreate(ctx, config, hostConfig, nil, nil, step.Name)
 	}

shared/utils/strings.go

@@ -15,20 +15,24 @@
 package utils
 
 // DedupStrings deduplicate string list, empty items are dropped
-func DedupStrings(list []string) []string {
+func DedupStrings(src []string) []string {
-	m := make(map[string]struct{}, len(list))
+	m := make(map[string]struct{}, len(src))
+	dst := make([]string, 0, len(src))
 
-	for i := range list {
+	for _, v := range src {
-		if s := list[i]; len(s) > 0 {
+		// Skip empty items
-			m[list[i]] = struct{}{}
+		if len(v) == 0 {
+			continue
 		}
+		// Skip duplicates
+		if _, ok := m[v]; ok {
+			continue
+		}
+		m[v] = struct{}{}
+		dst = append(dst, v)
 	}
 
-	newList := make([]string, 0, len(m))
+	return dst
-	for k := range m {
-		newList = append(newList, k)
-	}
-	return newList
 }
 
 // EqualStringSlice compare two string slices if they have equal values independent of how they are sorted