feat: add --pipeline-dirs flag to build command (#2323)

* feat: add --pipeline-dirs flag to build command

Adds --pipeline-dirs flag to accept multiple pipeline directories,
matching the test command functionality. The existing --pipeline-dir
(singular) is kept for backward compatibility.

Directories are searched in order with first match winning. For example,
if both custom1/fetch.yaml and custom2/fetch.yaml exist, custom1 wins:

  melange build --pipeline-dirs custom1 --pipeline-dirs custom2 --pipeline-dir original config.yaml
  # Searches: original/ -> custom1/ -> custom2/ -> /usr/share/melange/pipelines/

This enables layered pipeline overrides for teams with shared repositories.

Search order:
1. --pipeline-dir value (if specified)| (for backward compatibility)
2. --pipeline-dirs values (left to right)
3. Built-in pipeline directory

Signed-off-by: Debasish Biswas <debasishbsws.dev@gmail.com>

* update the docs

Signed-off-by: Debasish Biswas <debasishbsws.dev@gmail.com>

---------

Signed-off-by: Debasish Biswas <debasishbsws.dev@gmail.com>

Author: debasishbsws

docs/md/melange_build.md

@@ -62,6 +62,7 @@ melange build [flags]
       --package-append strings                                  extra packages to install for each of the build environments
       --persist-lint-results                                    persist lint results to JSON files in packages/{arch}/ directory
       --pipeline-dir string                                     directory used to extend defined built-in pipelines
+      --pipeline-dirs strings                                   directories used to extend defined built-in pipelines
   -r, --repository-append strings                               path to extra repositories to include in the build environment
       --rm                                                      clean up intermediate artifacts (e.g. container images, temp dirs) (default true)
       --runner string                                           which runner to use to enable running commands, default is based on your platform. Options are ["bubblewrap" "docker" "qemu"]

pkg/cli/build.go

@@ -47,6 +47,7 @@ func addBuildFlags(fs *pflag.FlagSet, flags *BuildFlags) {
 	fs.StringVar(&flags.BuildDate, "build-date", "", "date used for the timestamps of the files inside the image")
 	fs.StringVar(&flags.WorkspaceDir, "workspace-dir", "", "directory used for the workspace at /home/build")
 	fs.StringVar(&flags.PipelineDir, "pipeline-dir", "", "directory used to extend defined built-in pipelines")
+	fs.StringSliceVar(&flags.PipelineDirs, "pipeline-dirs", []string{}, "directories used to extend defined built-in pipelines")
 	fs.StringVar(&flags.SourceDir, "source-dir", "", "directory used for included sources")
 	fs.StringVar(&flags.CacheDir, "cache-dir", "./melange-cache/", "directory used for cached inputs")
 	fs.StringVar(&flags.CacheSource, "cache-source", "", "directory or bucket used for preloading the cache")
@@ -97,6 +98,7 @@ type BuildFlags struct {
 	BuildDate            string
 	WorkspaceDir         string
 	PipelineDir          string
+	PipelineDirs         []string
 	SourceDir            string
 	CacheDir             string
 	CacheSource          string
@@ -191,9 +193,9 @@ func (flags *BuildFlags) BuildOptions(ctx context.Context, args ...string) ([]bu
 		build.WithBuildDate(flags.BuildDate),
 		build.WithWorkspaceDir(flags.WorkspaceDir),
 		// Order matters, so add any specified pipelineDir before
-		// builtin pipelines.
+		// builtin pipelines. Support both --pipeline-dir (singular, deprecated)
+		// and --pipeline-dirs (plural, new). --pipeline-dir is processed first.
 		build.WithPipelineDir(flags.PipelineDir),
-		build.WithPipelineDir(BuiltinPipelineDir),
 		build.WithCacheDir(flags.CacheDir),
 		build.WithCacheSource(flags.CacheSource),
 		build.WithPackageCacheDir(flags.ApkCacheDir),
@@ -244,6 +246,13 @@ func (flags *BuildFlags) BuildOptions(ctx context.Context, args ...string) ([]bu
 		opts = append(opts, build.WithSourceDir(flags.SourceDir))
 	}
 
+	// Add multiple pipeline directories from --pipeline-dirs
+	for i := range flags.PipelineDirs {
+		opts = append(opts, build.WithPipelineDir(flags.PipelineDirs[i]))
+	}
+	// Always append built-in pipeline directory as fallback
+	opts = append(opts, build.WithPipelineDir(BuiltinPipelineDir))
+
 	if auth, ok := os.LookupEnv("HTTP_AUTH"); !ok {
 		// Fine, no auth.
 	} else if parts := strings.SplitN(auth, ":", 4); len(parts) != 4 {