fix: add option to set additional build contexts (#116)

_docs/data/data.yaml

@@ -89,6 +89,11 @@ properties:
     type: string
     required: false
 
+  named_context:
+    description: Set additional named [build contexts](https://docs.docker.com/engine/reference/commandline/buildx_build/#build-context) (e.g., name=path).
+    type: list
+    required: false
+
   tags:
     description: Set repository tags to use for the image. Tags can also be loaded from a `.tags` file.
     defaultValue: latest

cmd/drone-docker-buildx/config.go

@@ -128,6 +128,13 @@ func settingsFlags(settings *plugin.Settings, category string) []cli.Flag {
 			Destination: &settings.Build.Context,
 			Category:    category,
 		},
+		&cli.StringSliceFlag{
+			Name:        "named-context",
+			EnvVars:     []string{"PLUGIN_NAMED_CONTEXT"},
+			Usage:       "additional named build context",
+			Destination: &settings.Build.NamedContext,
+			Category:    category,
+		},
 		&cli.StringSliceFlag{
 			Name:        "tags",
 			EnvVars:     []string{"PLUGIN_TAG", "PLUGIN_TAGS"},

plugin/docker.go

@@ -117,6 +117,9 @@ func commandBuild(build Build, dryrun bool) *exec.Cmd {
 	if build.Output != "" {
 		args = append(args, "--output", build.Output)
 	}
+	for _, arg := range build.NamedContext.Value() {
+		args = append(args, "--build-context", arg)
+	}
 
 	if len(build.Platforms.Value()) > 0 {
 		args = append(args, "--platform", strings.Join(build.Platforms.Value(), ","))

plugin/impl.go

@@ -59,6 +59,7 @@ type Build struct {
 	AddHost      cli.StringSlice // Docker build add-host
 	Quiet        bool            // Docker build quiet
 	Output       string          // Docker build output folder
+	NamedContext cli.StringSlice // Docker build named context
 }
 
 // Settings for the Plugin.