feat: ability to skip Homebrew Tap update for preleases (#943)

- Updates Homebrew config to make "SkipUpload" a string so that it can
  contain more than true or false values. New available options are
  "true", "false" and "auto".
- Adds a new check in Homebrew publish to see if it should skip due to a
  prerelease and "SkipUpload" set to auto.
- Adds a new test to make sure that tap publishing is skipped when set
  to "auto" and a prerelease semver is provided.
- Updates documents to add information about the new "auto" option for
  "SkipUpload".

internal/pipe/brew/brew.go

@@ -122,7 +122,7 @@ func doRun(ctx *context.Context, client client.Client) error {
 		return err
 	}
 
-	if ctx.Config.Brew.SkipUpload {
+	if strings.TrimSpace(ctx.Config.Brew.SkipUpload) == "true" {
 		return pipe.Skip("brew.skip_upload is set")
 	}
 	if ctx.SkipPublish {
@@ -131,6 +131,9 @@ func doRun(ctx *context.Context, client client.Client) error {
 	if ctx.Config.Release.Draft {
 		return pipe.Skip("release is marked as draft")
 	}
+	if strings.TrimSpace(ctx.Config.Brew.SkipUpload) == "auto" && ctx.Semver.Prerelease != "" {
+		return pipe.Skip("prerelease detected with 'auto' upload, skipping homebrew publish")
+	}
 
 	var gpath = ghFormulaPath(ctx.Config.Brew.Folder, filename)
 	log.WithField("formula", gpath).

internal/pipe/brew/brew_test.go

@@ -313,22 +313,34 @@ func TestRunPipeNoUpload(t *testing.T) {
 	}
 	t.Run("skip upload", func(tt *testing.T) {
 		ctx.Config.Release.Draft = false
-		ctx.Config.Brew.SkipUpload = true
+		ctx.Config.Brew.SkipUpload = "true"
 		ctx.SkipPublish = false
 		assertNoPublish(tt)
 	})
 	t.Run("skip publish", func(tt *testing.T) {
 		ctx.Config.Release.Draft = false
-		ctx.Config.Brew.SkipUpload = false
+		ctx.Config.Brew.SkipUpload = "false"
 		ctx.SkipPublish = true
 		assertNoPublish(tt)
 	})
 	t.Run("draft release", func(tt *testing.T) {
 		ctx.Config.Release.Draft = true
-		ctx.Config.Brew.SkipUpload = false
+		ctx.Config.Brew.SkipUpload = "false"
 		ctx.SkipPublish = false
 		assertNoPublish(tt)
 	})
+	t.Run("skip prerelease publish", func(tt *testing.T) {
+		ctx.Config.Release.Draft = false
+		ctx.Config.Brew.SkipUpload = "auto"
+		ctx.SkipPublish = false
+		ctx.Semver = context.Semver{
+			Major:      1,
+			Minor:      0,
+			Patch:      0,
+			Prerelease: "rc1",
+		}
+		assertNoPublish(tt)
+	})
 }
 
 func TestRunPipeFormatBinary(t *testing.T) {

pkg/config/config.go

@@ -48,7 +48,7 @@ type Homebrew struct {
 	Conflicts        []string     `yaml:",omitempty"`
 	Description      string       `yaml:",omitempty"`
 	Homepage         string       `yaml:",omitempty"`
-	SkipUpload       bool         `yaml:"skip_upload,omitempty"`
+	SkipUpload       string       `yaml:"skip_upload,omitempty"`
 	DownloadStrategy string       `yaml:"download_strategy,omitempty"`
 	SourceTarball    string       `yaml:"-"`
 	URLTemplate      string       `yaml:"url_template,omitempty"`

www/content/homebrew.md

@@ -37,7 +37,7 @@ brew:
 
   # Allows you to add a custom require_relative at the top of the formula template
   # Default is empty
-  custom_require: custom_download_strategy 
+  custom_require: custom_download_strategy
 
   # Git author used to commit to the repository.
   # Defaults are shown.
@@ -64,6 +64,8 @@ brew:
   # Setting this will prevent goreleaser to actually try to commit the updated
   # formula - instead, the formula file will be stored on the dist folder only,
   # leaving the responsibility of publishing it to the user.
+  # If set to auto, the release will not be uploaded to the homebrew tap
+  # in case there is an indicator for prerelease in the tag e.g. v1.0.0-rc1
   # Default is false.
   skip_upload: true