Avoid building manifests in nested directories

... when changes were made to parent directory as well. This will
prevent building same manifests multiple times as only the manifest of
the parent directory will be built.

Author: DTLP

README.md

@@ -21,15 +21,16 @@ Usage:
 
     NAME:
        kustomize-build-dirs - Given a list of input files, run `kustomize build` somewhere
-    
+
     USAGE:
-       kustomize-build-dirs [global options] command [command options] 
-    
+       kustomize-build-dirs [global options] command [command options]
+
     COMMANDS:
        help, h  Shows a list of commands or help for one command
-    
+
     GLOBAL OPTIONS:
        --out-dir value     Directory to output build manifests
+       --depth value       Minimum directory depth to work with (e.g., 2 means paths will be at least two levels deep like 'aaa/bbb/') (default: 0)
        --truncate-secrets  Whether or not to truncate secrets. This can make life easier when you don't have strongbox credentials for some secrets (default: false)
        --help, -h          show help
 
@@ -47,6 +48,45 @@ in 'manifests.yaml' there. For example, if there is a kustomize directory at
 Will result in the built manifests being placed at
 'build/project-manifests/manifests.yaml'
 
+Passing the `--depth` flag will set a minimum directory depth for kustomize
+directories to be processed. If a directory’s depth is less than the specified
+depth value, it will be ignored and no manifests will be built for it.
+
+For example, you made changes to the following files:
+
+```
+cluster-a/
+└── file.yaml
+cluster-b/
+├── namespace-a/
+|   ├── file.yaml
+|   └── app-a/
+|       └── file.yaml
+└── namespace-b/
+    └── file.yaml
+cluster-c/
+└── namespace-a/
+    └── app-a/
+        └── file.yaml
+```
+
+and run
+
+```
+kustomize-build-dirs --out-dir build --depth 2 project-manifests
+```
+
+the result manifests built will only include
+
+```
+build/
+├── cluster-b/
+|   ├── namespace-a/
+|   └── namespace-b/
+└── cluster-c/
+    └── namesapce-a/
+```
+
 Passing the `--truncate-secrets` flag will cause the application to empty any
 files that look to be [`strongbox`](https://github.com/uw-labs/strongbox)
 encrypted before running `kustomize build`, so the contents of any secrets will

cmd/kustomize-build-dirs/main.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"sort"
 	"strings"
 	"sync"
 
@@ -29,6 +30,7 @@ var getwdFunc = os.Getwd
 func main() { //go-cov:skip
 	var opts struct {
 		outDir            string
+		dirDepth          int
 		doTruncateSecrets bool
 	}
 	app := &cli.App{
@@ -41,6 +43,12 @@ func main() { //go-cov:skip
 				Usage:       "Directory to output build manifests",
 				Destination: &opts.outDir,
 			},
+			&cli.IntFlag{
+				Name:        "depth",
+				Value:       0,
+				Usage:       "Minimum directory depth to work with (e.g., 2 means paths will be at least two levels deep like 'aaa/bbb/')",
+				Destination: &opts.dirDepth,
+			},
 			&cli.BoolFlag{
 				Name:        "truncate-secrets",
 				Value:       false,
@@ -49,7 +57,12 @@ func main() { //go-cov:skip
 			},
 		},
 		Action: func(c *cli.Context) error {
-			return kustomizeBuildDirs(opts.outDir, opts.doTruncateSecrets, c.Args().Slice())
+			return kustomizeBuildDirs(
+				opts.outDir,
+				opts.dirDepth,
+				opts.doTruncateSecrets,
+				c.Args().Slice(),
+			)
 		},
 	}
 
@@ -59,7 +72,12 @@ func main() { //go-cov:skip
 	}
 }
 
-func kustomizeBuildDirs(outDir string, doTruncateSecrets bool, filepaths []string) error {
+func kustomizeBuildDirs(
+	outDir string,
+	dirDepth int,
+	doTruncateSecrets bool,
+	filepaths []string,
+) error {
 	rootDir, err := getwdFunc()
 	if err != nil {
 		return fmt.Errorf("error reading working directory: %v", err)
@@ -69,7 +87,7 @@ func kustomizeBuildDirs(outDir string, doTruncateSecrets bool, filepaths []strin
 		return err
 	}
 
-	kustomizationRoots, err := findKustomizationRoots(rootDir, filepaths)
+	kustomizationRoots, err := findKustomizationRoots(rootDir, filepaths, dirDepth)
 	if err != nil {
 		return err
 	}
@@ -109,10 +127,103 @@ func checkKustomizeInstalled() error {
 	return nil
 }
 
+// splitPath takes a full file path string and returns a slice of its directory components.
+// It extracts the directory portion of the path and splits it by forward slashes (/).
+// Example: "aaa/bbb/ccc/file.yaml" => ["aaa", "bbb", "ccc"]
+func splitPath(path string) []string {
+	cleaned := filepath.ToSlash(filepath.Dir(path))
+	if cleaned == "." {
+		return []string{}
+	}
+	return strings.Split(cleaned, "/")
+}
+
+// commonPrefix compares two string slices (representing directory segments)
+// and returns their longest shared prefix.
+// Example: ["aaa", "bbb", "ccc"], ["aaa", "bbb", "ddd"] => ["aaa", "bbb"]
+func commonPrefix(a, b []string) []string {
+	minLen := len(a)
+	if len(b) < minLen {
+		minLen = len(b)
+	}
+	out := make([]string, 0, minLen)
+	for i := 0; i < minLen; i++ {
+		if a[i] != b[i] {
+			break
+		}
+		out = append(out, a[i])
+	}
+	return out
+}
+
+// deepestCommonDirs takes a list of file paths and returns a list of directory paths
+// that represent the deepest common directory for each group of similarly prefixed files
+// with a minimum directory depth enforced.
+// Example (with minDepth = 2):
+// Input: ["aaa/file.yaml", "aaa/bbb/file.yaml", "bbb/ccc/file1.yaml", "bbb/ccc/file2.yaml"]
+// Output: ["aaa/bbb/", "bbb/ccc/"]
+func deepestCommonDirs(paths []string, minDepth int) []string {
+	if len(paths) == 0 {
+		return nil
+	}
+
+	dirSet := make(map[string]struct{})
+
+	for _, path := range paths {
+		dir := filepath.ToSlash(filepath.Dir(path))
+		if dir == "." {
+			// File in root directory is represented as empty string
+			dir = ""
+		}
+		dirSet[dir] = struct{}{}
+	}
+
+	// Filter out directories that are shallower than minDepth
+	var dirs []string
+	for dir := range dirSet {
+		segments := strings.Split(dir, "/")
+		if dir == "" {
+			segments = []string{}
+		}
+		if len(segments) >= minDepth {
+			dirs = append(dirs, dir)
+		}
+	}
+	sort.Strings(dirs) // Sort for consistent and hierarchical comparison
+
+	var result []string
+	skipPrefixes := make(map[string]struct{})
+
+	for _, dir := range dirs {
+		skip := false
+
+		for parent := range skipPrefixes {
+			if strings.HasPrefix(dir+"/", parent+"/") {
+				skip = true
+				break
+			}
+		}
+
+		if !skip {
+			skipPrefixes[dir] = struct{}{}
+			if dir == "" {
+				result = append(result, "")
+			} else {
+				result = append(result, dir+"/")
+			}
+		}
+	}
+
+	return result
+}
+
 // findKustomizationRoots finds, for each given path, the first parent
 // directory containing a 'kustomization.yaml'. It returns a list of such paths
 // relative to the root
-func findKustomizationRoots(root string, paths []string) ([]string, error) {
+func findKustomizationRoots(root string, paths []string, dirDepth int) ([]string, error) {
+	// Group paths by shared prefixes and return their deepest common directories
+	paths = deepestCommonDirs(paths, dirDepth)
+
 	// there may be multiple changes under the same path
 	// so use a map to track unique ones
 	rootsMap := map[string]struct{}{}