feat: infer app dependencies for change-based rendering

cmd/main.go

@@ -90,6 +90,8 @@ func run(cfg *Config) error {
 		FilesChanged:               filesChanged,
 		IgnoreInvalidWatchPattern:  cfg.IgnoreInvalidWatchPattern,
 		WatchIfNoWatchPatternFound: cfg.WatchIfNoWatchPatternFound,
+		InferAppDependencies:       cfg.InferAppDependencies,
+		RepoSelector:               cfg.RepoSelector,
 	}
 
 	// Get applications for both branches

cmd/options.go

@@ -71,6 +71,7 @@ var (
 	DefaultDryRun                               = false
 	DefaultAutoDetectFilesChanged               = true
 	DefaultWatchIfNoWatchPatternFound           = true
+	DefaultInferAppDependencies                 = false
 	DefaultIgnoreInvalidWatchPattern            = false
 	DefaultHideDeletedAppDiff                   = false
 	DefaultIgnoreResourceRules                  = ""
@@ -112,6 +113,7 @@ type RawOptions struct {
 	FilesChanged                         string `mapstructure:"files-changed"`
 	IgnoreInvalidWatchPattern            bool   `mapstructure:"ignore-invalid-watch-pattern"`
 	WatchIfNoWatchPatternFound           bool   `mapstructure:"watch-if-no-watch-pattern-found"`
+	InferAppDependencies                 bool   `mapstructure:"infer-app-dependencies"`
 	AutoDetectFilesChanged               bool   `mapstructure:"auto-detect-files-changed"`
 	KeepClusterAlive                     bool   `mapstructure:"keep-cluster-alive"`
 	ArgocdNamespace                      string `mapstructure:"argocd-namespace"`
@@ -159,6 +161,7 @@ type Config struct {
 	MaxDiffLength                        uint
 	IgnoreInvalidWatchPattern            bool
 	WatchIfNoWatchPatternFound           bool
+	InferAppDependencies                 bool
 	AutoDetectFilesChanged               bool
 	KeepClusterAlive                     bool
 	ArgocdNamespace                      string
@@ -252,6 +255,7 @@ func Parse() *Config {
 	viper.SetDefault("secrets-folder", DefaultSecretsFolder)
 	viper.SetDefault("create-cluster", DefaultCreateCluster)
 	viper.SetDefault("watch-if-no-watch-pattern-found", DefaultWatchIfNoWatchPatternFound)
+	viper.SetDefault("infer-app-dependencies", DefaultInferAppDependencies)
 	viper.SetDefault("ignore-invalid-watch-pattern", DefaultIgnoreInvalidWatchPattern)
 	viper.SetDefault("keep-cluster-alive", DefaultKeepClusterAlive)
 	viper.SetDefault("cluster", DefaultCluster)
@@ -330,6 +334,7 @@ func Parse() *Config {
 	rootCmd.Flags().Bool("auto-detect-files-changed", DefaultAutoDetectFilesChanged, "Auto detect files changed between branches")
 	rootCmd.Flags().Bool("ignore-invalid-watch-pattern", DefaultIgnoreInvalidWatchPattern, "Ignore invalid watch pattern Regex on Applications")
 	rootCmd.Flags().Bool("watch-if-no-watch-pattern-found", DefaultWatchIfNoWatchPatternFound, "Render applications without watch pattern")
+	rootCmd.Flags().Bool("infer-app-dependencies", DefaultInferAppDependencies, "Infer each application's local-repo file dependencies (spec.source.path and helm.valueFiles) and render it only when those files change. Combine with --watch-if-no-watch-pattern-found=false to render only affected applications")
 	rootCmd.Flags().String("redirect-target-revisions", "", "Comma-separated source targetRevision values to redirect to the target branch. Example: main,HEAD. By default, every targetRevision in matching repositories is redirected")
 	rootCmd.Flags().String("title", DefaultTitle, "Custom title for the markdown output")
 	rootCmd.Flags().Bool("hide-deleted-app-diff", DefaultHideDeletedAppDiff, "Hide diff content for fully deleted applications (only show deletion header)")
@@ -406,6 +411,7 @@ func (o *RawOptions) ToConfig() (*Config, error) {
 		MaxDiffLength:                        o.MaxDiffLength,
 		IgnoreInvalidWatchPattern:            o.IgnoreInvalidWatchPattern,
 		WatchIfNoWatchPatternFound:           o.WatchIfNoWatchPatternFound,
+		InferAppDependencies:                 o.InferAppDependencies,
 		AutoDetectFilesChanged:               o.AutoDetectFilesChanged,
 		KeepClusterAlive:                     o.KeepClusterAlive,
 		ArgocdNamespace:                      o.ArgocdNamespace,
@@ -717,6 +723,9 @@ func (o *Config) LogConfig() {
 		} else {
 			log.Info().Msgf("✨ --- Skip applications with no watch-pattern annotation")
 		}
+		if o.InferAppDependencies {
+			log.Info().Msgf("✨ --- Infer application dependencies from spec.source.path and helm.valueFiles")
+		}
 	}
 	if len(o.Selectors) > 0 {
 		selectorStrings := make([]string, len(o.Selectors))

docs/application-selection.md

@@ -128,6 +128,28 @@ spec:
 
 For more details on this annotation, see the [Argo CD documentation](https://argo-cd.readthedocs.io/en/stable/operator-manual/high_availability/#manifest-paths-annotation).
 
+### Option C: Automatic Dependency Inference
+
+Both options above require you to declare each application's dependencies via annotations. The `--infer-app-dependencies` flag removes that requirement: instead of reading annotations, the tool inspects each application's own spec and derives the repository files it depends on, then renders the application only when one of those files changes.
+
+**What is inferred (for sources that live in the repository being diffed):**
+
+- `spec.source.path` / `spec.sources[*].path` — the application is rendered when any changed file falls under that directory. This is source-type agnostic: it works for Helm, Kustomize, plain manifest directories, jsonnet, etc.
+- `helm.valueFiles` — individual values files, resolved relative to the source path. References to another source via `$ref/...` (for example `$values/env/prod.yaml`) are resolved against that ref source, so a **remote Helm chart whose values come from a local source** is still rendered when the local values file changes.
+
+**What is not inferred:** files that do not live in this repository (remote chart contents, cross-repo sources) cannot be tracked — the tool only has this repository checked out. Such applications fall back to the `--watch-if-no-watch-pattern-found` setting. Kustomize bases referenced via `../` outside `source.path` are also not traced.
+
+Inferred dependencies are combined with any `watch-pattern` / `manifest-generate-paths` annotations (union — an application renders if either matches), and the application is always rendered if its own manifest file changes.
+
+**Usage** — combine with `--watch-if-no-watch-pattern-found=false` so applications with no changed dependencies are skipped:
+
+```bash
+argocd-diff-preview --infer-app-dependencies --watch-if-no-watch-pattern-found=false
+```
+
+!!! note "ApplicationSets"
+    When `--infer-app-dependencies` is enabled, ApplicationSets are always generated (they are not pre-filtered by changed files), and the resulting Applications are then filtered by their inferred dependencies. This means you no longer need `watch-pattern` annotations on the ApplicationSet template — but every non-excluded ApplicationSet is generated on each run (generation is cheap relative to rendering). `render: "never"`, the `ignore` annotation, and label selectors still apply to ApplicationSets as usual.
+
 ### Implementing Changed File Detection in CI/CD
 
 Once you've added watch-pattern annotations to your applications, configure your CI/CD pipeline to detect changed files and use them for filtering. Here are two approaches:

docs/options.md

@@ -23,6 +23,7 @@ argocd-diff-preview [FLAGS] [OPTIONS] (--repo <repo> | --repo-regex <regex>) --t
 | `--disable-client-throttling`       | `DISABLE_CLIENT_THROTTLING`       | `true`  | Disable client-side throttling (rely on API Priority and Fairness instead)                                                       |
 | `--auto-detect-files-changed`       | `AUTO_DETECT_FILES_CHANGED`       | `true`  | Auto detect files changed between branches. Skipped if `--files-changed` is provided                                             |
 | `--watch-if-no-watch-pattern-found` | `WATCH_IF_NO_WATCH_PATTERN_FOUND` | `true`  | Render applications without watch-pattern annotation                                                                             |
+| `--infer-app-dependencies`          | `INFER_APP_DEPENDENCIES`          | `false` | Infer each application's local-repo file dependencies (`spec.source.path` and `helm.valueFiles`) and render it only when those files change. Combine with `--watch-if-no-watch-pattern-found=false` |
 | `--debug`, `-d`                     | `DEBUG`                           | `false` | Activate debug mode                                                                                                              |
 | `--dry-run`                         | `DRY_RUN`                         | `false` | Show which applications would be processed without creating a cluster or generating a diff                                       |
 | `--hide-deleted-app-diff`           | `HIDE_DELETED_APP_DIFF`           | `false` | Hide diff content for deleted applications (only show deletion header)                                                           |