feat: image names can ontain template variables

This now allows us to use things like the ProjectName as variables
in our docker image name. This is especially helpful when trying to
make the `.goreleaser.yml` as generic as possible.

internal/pipe/docker/docker.go

@@ -44,7 +44,7 @@ func (Pipe) Default(ctx *context.Context) error {
 			docker.Goarch = "amd64"
 		}
 	}
-	// only set defaults if there is exacly 1 docker setup in the config file.
+	// only set defaults if there is exactly 1 docker setup in the config file.
 	if len(ctx.Config.Dockers) != 1 {
 		return nil
 	}
@@ -102,7 +102,7 @@ func doRun(ctx *context.Context) error {
 func process(ctx *context.Context, docker config.Docker, artifact artifact.Artifact) error {
 	tmp, err := ioutil.TempDir(ctx.Config.Dist, "goreleaserdocker")
 	if err != nil {
-		return errors.Wrap(err, "failed to create temporaty dir")
+		return errors.Wrap(err, "failed to create temporary dir")
 	}
 	log.Debug("tempdir: " + tmp)
 
@@ -143,14 +143,15 @@ func processTagTemplates(ctx *context.Context, docker config.Docker, artifact ar
 	// nolint:prealloc
 	var images []string
 	for _, tagTemplate := range docker.TagTemplates {
+		imageTemplate := fmt.Sprintf("%s:%s", docker.Image, tagTemplate)
 		// TODO: add overrides support to config
-		tag, err := tmpl.New(ctx).
+		image, err := tmpl.New(ctx).
 			WithArtifact(artifact, map[string]string{}).
-			Apply(tagTemplate)
+			Apply(imageTemplate)
 		if err != nil {
 			return nil, errors.Wrapf(err, "failed to execute tag template '%s'", tagTemplate)
 		}
-		images = append(images, fmt.Sprintf("%s:%s", docker.Image, tag))
+		images = append(images, image)
 	}
 	return images, nil
 }

internal/pipe/docker/docker_test.go

@@ -384,7 +384,7 @@ func TestRunPipe(t *testing.T) {
 				},
 			},
 			assertImageLabels: noLabels,
-			assertError:       shouldErr(`template: tmpl:1:6: executing "tmpl" at <.Env.NOPE>: map has no entry for key "NOPE"`),
+			assertError:       shouldErr(`template: tmpl:1:46: executing "tmpl" at <.Env.NOPE>: map has no entry for key "NOPE"`),
 		},
 		"missing_env_on_build_flag_template": {
 			publish: true,
@@ -406,6 +406,36 @@ func TestRunPipe(t *testing.T) {
 			assertImageLabels: noLabels,
 			assertError:       shouldErr(`template: tmpl:1:19: executing "tmpl" at <.Env.NOPE>: map has no entry for key "NOPE"`),
 		},
+		"image_has_projectname_template_variable": {
+			publish: true,
+			dockers: []config.Docker{
+				{
+					Image:      registry + "goreleaser/{{.ProjectName}}",
+					Goos:       "linux",
+					Goarch:     "amd64",
+					Dockerfile: "testdata/Dockerfile",
+					Binary:     "mybin",
+					SkipPush:   true,
+					TagTemplates: []string{
+						"{{.Tag}}-{{.Env.FOO}}",
+						"v{{.Major}}",
+						"v{{.Major}}.{{.Minor}}",
+						"latest",
+					},
+					Files: []string{
+						"testdata/extra_file.txt",
+					},
+				},
+			},
+			expect: []string{
+				registry + "goreleaser/mybin:v1.0.0-123",
+				registry + "goreleaser/mybin:v1",
+				registry + "goreleaser/mybin:v1.0",
+				registry + "goreleaser/mybin:latest",
+			},
+			assertImageLabels: noLabels,
+			assertError:       shouldNotErr,
+		},
 		"no_permissions": {
 			publish: true,
 			dockers: []config.Docker{

www/content/docker.md

@@ -84,6 +84,23 @@ These settings should allow you to generate multiple Docker images,
 for example, using multiple `FROM` statements,
 as well as generate one image for each binary in your project.
 
+## Generic Image Names
+
+Some users might want to keep their image name as generic as possible.
+That can be accomplished simply by adding template language in the definition:
+
+```yaml
+# .goreleaser.yml
+dockers:
+  -
+    binary: mybinary
+    image: myuser/{{.ProjectName}}
+```
+
+This will build and public the following images:
+
+- `myuser/mybinary`
+
 ## Keeping docker images updated for current major
 
 Some users might want to when version to push docker tags `:v1`, `:v1.6`,