[cli] Delete --root flag

It's been replaced by the -C flag, and can be removed entirely after all
downstream usages have been fixed.

Change-Id: Id3e98914e5dceb65a5715e8102b05451c0fa2aa5
Reviewed-on: https://fuchsia-review.googlesource.com/c/shac-project/shac/+/914338
Reviewed-by: Anthony Fandrianto <atyfto@google.com>
Fuchsia-Auto-Submit: Oliver Newman <olivernewman@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
diff --git a/internal/cli/base.go b/internal/cli/base.go
index 97f7e5a..716216b 100644
--- a/internal/cli/base.go
+++ b/internal/cli/base.go
@@ -22,7 +22,6 @@
 )
 
 type commandBase struct {
-	root      string
 	cwd       string
 	allFiles  bool
 	noRecurse bool
@@ -35,27 +34,14 @@
 	f.BoolVar(&c.noRecurse, "no-recurse", false, "do not look for shac.star files recursively")
 	c.vars = stringMapFlag{}
 	f.Var(&c.vars, "var", "runtime variables to set, of the form key=value")
-
-	// TODO(olivernewman): Delete this flag after it's no longer used.
-	f.StringVar(&c.root, "root", ".", "path to the root of the tree to analyse")
-	// MarkHidden instead of MarkDeprecated to prevent warnings from being
-	// emitted.
-	f.MarkHidden("root")
 }
 
 func (c *commandBase) options(files []string) (engine.Options, error) {
 	if c.allFiles && len(files) > 0 {
 		return engine.Options{}, errors.New("--all cannot be set together with positional file arguments")
 	}
-	cwd := c.cwd
-	if c.root != "." {
-		if cwd != "." {
-			return engine.Options{}, errors.New("--root and --cwd cannot both be set")
-		}
-		cwd = c.root
-	}
 	return engine.Options{
-		Dir:      cwd,
+		Dir:      c.cwd,
 		AllFiles: c.allFiles,
 		Files:    files,
 		Recurse:  !c.noRecurse,