Revert "Remove docs for Strict Mode and --strict flag (ko-build#210)"

This reverts commit d7b989a.

README.md

@@ -268,6 +268,19 @@ of convenience for cleaning up resources created through `ko apply`.
 `ko version` prints version of ko. For not released binaries it will print hash
 of latest commit in current git tree.
 
+### Strict Mode
+
+It can be difficult for `ko` to determine whether a string in a YAML file is
+intended to be an import path, due to typos, non-`package main` packages, and
+conflicts between import paths and common strings (e.g., a package whose import
+path is `busybox`). To solve this, `ko` supports "Strict Mode".
+
+When referencing an import path in the YAML file, prefix the string with the
+string `ko://` (e.g., `ko://github.com/my/repo/cmd/foo`). Then, when calling
+`ko apply` or `ko resolve`, pass `--strict`. If a string with the `ko://` prefix
+is not determined to be a valid import path, the command will fail, rather than
+passing it through to the resolved YAML.
+
 ## With `minikube`
 
 You can use `ko` with `minikube` via a Docker Registry, but this involves

pkg/commands/apply.go

@@ -147,6 +147,7 @@ func addApply(topLevel *cobra.Command) {
 	options.AddPublishArg(apply, po)
 	options.AddFileArg(apply, fo)
 	options.AddSelectorArg(apply, so)
+	options.AddStrictArg(apply, sto)
 	options.AddBuildOptions(apply, bo)
 
 	// Collect the ko-specific apply flags before registering the kubectl global

pkg/commands/create.go

@@ -147,6 +147,7 @@ func addCreate(topLevel *cobra.Command) {
 	options.AddPublishArg(create, po)
 	options.AddFileArg(create, fo)
 	options.AddSelectorArg(create, so)
+	options.AddStrictArg(create, sto)
 	options.AddBuildOptions(create, bo)
 
 	// Collect the ko-specific apply flags before registering the kubectl global

pkg/commands/options/strict.go

@@ -14,7 +14,16 @@
 
 package options
 
+import (
+	"github.com/spf13/cobra"
+)
+
 // StrictOptions holds options to require strict references.
 type StrictOptions struct {
 	Strict bool
 }
+
+func AddStrictArg(cmd *cobra.Command, so *StrictOptions) {
+	cmd.Flags().BoolVarP(&so.Strict, "strict", "", so.Strict,
+		`If true, require package references to be explicitly prefixed with "ko://"`)
+}

pkg/commands/resolve.go

@@ -74,6 +74,7 @@ func addResolve(topLevel *cobra.Command) {
 	options.AddPublishArg(resolve, po)
 	options.AddFileArg(resolve, fo)
 	options.AddSelectorArg(resolve, so)
+	options.AddStrictArg(resolve, sto)
 	options.AddBuildOptions(resolve, bo)
 	topLevel.AddCommand(resolve)
 }