feat: Join() reclaimed for strings — ErrorJoin for errors

core.Join("/", "deploy", "to", "homelab") → "deploy/to/homelab"
core.Join(".", "cmd", "deploy", "description") → "cmd.deploy.description"

Join builds via Concat — same hook point for security/validation.
errors.Join wrapper renamed to ErrorJoin.
JoinPath now delegates to Join("/", ...).

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/core/command.go

@@ -184,7 +184,7 @@ func (c *Core) Command(args ...any) any {
 		// Build parent chain — "deploy/to/homelab" creates "deploy" and "deploy/to" if missing
 		parts := Split(path, "/")
 		for i := len(parts) - 1; i > 0; i-- {
-			parentPath := StringJoin(parts[:i], "/")
+			parentPath := JoinPath(parts[:i]...)
 			if _, exists := c.commands.commands[parentPath]; !exists {
 				c.commands.commands[parentPath] = &Command{
 					name:     parts[i-1],

pkg/core/error.go

@@ -138,9 +138,10 @@ func NewError(text string) error {
 	return errors.New(text)
 }
 
-// Join combines multiple errors into one.
-// Wrapper around errors.Join for convenience.
-func Join(errs ...error) error {
+// ErrorJoin combines multiple errors into one.
+//
+//	core.ErrorJoin(err1, err2, err3)
+func ErrorJoin(errs ...error) error {
 	return errors.Join(errs...)
 }
 

pkg/core/string.go

@@ -60,11 +60,19 @@ func SplitN(s, sep string, n int) []string {
 	return strings.SplitN(s, sep, n)
 }
 
-// StringJoin joins segments with separator.
+// Join joins parts with a separator, building via Concat.
 //
-//	core.StringJoin([]string{"a", "b", "c"}, "/")  // "a/b/c"
-func StringJoin(elems []string, sep string) string {
-	return strings.Join(elems, sep)
+//	core.Join("/", "deploy", "to", "homelab")      // "deploy/to/homelab"
+//	core.Join(".", "cmd", "deploy", "description")  // "cmd.deploy.description"
+func Join(sep string, parts ...string) string {
+	if len(parts) == 0 {
+		return ""
+	}
+	result := parts[0]
+	for _, p := range parts[1:] {
+		result = Concat(result, sep, p)
+	}
+	return result
 }
 
 // Replace replaces all occurrences of old with new in s.

pkg/core/utils.go

@@ -26,7 +26,7 @@ func Print(w io.Writer, format string, args ...any) {
 //
 //	core.JoinPath("deploy", "to", "homelab")  // → "deploy/to/homelab"
 func JoinPath(segments ...string) string {
-	return StringJoin(segments, "/")
+	return Join("/", segments...)
 }
 
 // IsFlag returns true if the argument starts with a dash.

tests/error_test.go

@@ -187,10 +187,10 @@ func TestNewError_Good(t *testing.T) {
 	assert.Equal(t, "simple error", err.Error())
 }
 
-func TestJoin_Good(t *testing.T) {
+func TestErrorJoin_Good(t *testing.T) {
 	e1 := errors.New("first")
 	e2 := errors.New("second")
-	joined := Join(e1, e2)
+	joined := ErrorJoin(e1, e2)
 	assert.ErrorIs(t, joined, e1)
 	assert.ErrorIs(t, joined, e2)
 }

tests/string_test.go

@@ -43,8 +43,8 @@ func TestSplitN_Good(t *testing.T) {
 	assert.Equal(t, []string{"key", "value=extra"}, SplitN("key=value=extra", "=", 2))
 }
 
-func TestStringJoin_Good(t *testing.T) {
-	assert.Equal(t, "a/b/c", StringJoin([]string{"a", "b", "c"}, "/"))
+func TestJoin_Good(t *testing.T) {
+	assert.Equal(t, "a/b/c", Join("/", "a", "b", "c"))
 }
 
 func TestReplace_Good(t *testing.T) {