bib: fix injecting default "build" arg into root for flags like --local

In PR#608 we dropped the container entrypoint and moved the logic
to detect what command to run into the cobra parsing.

However it seems certain situations like:
```
bootc-image-builder  --type qcow2 --tls-verify=true  --local quay.io/centos-bootc/centos-bootc:stream10
```
are not detected correctly (thanka to Chunfu Wen for reporting!).

This commit detect this usage and injects the build arg then too.

Closes #614

bib/cmd/bootc-image-builder/export_test.go

@@ -9,6 +9,7 @@ var (
 	UpdateFilesystemSizes         = updateFilesystemSizes
 	GenPartitionTable             = genPartitionTable
 	CreateRand                    = createRand
+	BuildCobraCmdline             = buildCobraCmdline
 )
 
 func MockOsGetuid(new func() int) (restore func()) {

bib/cmd/bootc-image-builder/main.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 	"golang.org/x/exp/slices"
 
 	"github.com/osbuild/images/pkg/arch"
@@ -565,7 +566,7 @@ func cmdVersion(_ *cobra.Command, _ []string) error {
 	return nil
 }
 
-func run() error {
+func buildCobraCmdline() (*cobra.Command, error) {
 	rootCmd := &cobra.Command{
 		Use:               "bootc-image-builder",
 		Long:              "create a bootable image from an ostree native container",
@@ -612,7 +613,7 @@ func run() error {
 	// default from users.
 	manifestCmd.Flags().String("config", "", "build config file; /config.json will be used if present")
 	if err := manifestCmd.Flags().MarkHidden("config"); err != nil {
-		return fmt.Errorf("cannot hide 'config' :%w", err)
+		return nil, fmt.Errorf("cannot hide 'config' :%w", err)
 	}
 
 	buildCmd.Flags().AddFlagSet(manifestCmd.Flags())
@@ -626,11 +627,11 @@ func run() error {
 	// flag rules
 	for _, dname := range []string{"output", "store", "rpmmd"} {
 		if err := buildCmd.MarkFlagDirname(dname); err != nil {
-			return err
+			return nil, err
 		}
 	}
 	if err := buildCmd.MarkFlagFilename("config"); err != nil {
-		return err
+		return nil, err
 	}
 	buildCmd.MarkFlagsRequiredTogether("aws-region", "aws-bucket", "aws-ami-name")
 
@@ -640,11 +641,29 @@ func run() error {
 	// "quay.io" will create an "err != nil". Ideally we could check err
 	// for something like cobra.UnknownCommandError but cobra just gives
 	// us an error string
-	_, _, err := rootCmd.Find(os.Args[1:])
-	if err != nil && !slices.Contains([]string{"help", "completion"}, os.Args[1]) {
+	cmd, _, err := rootCmd.Find(os.Args[1:])
+	injectBuildArg := func() {
 		args := append([]string{buildCmd.Name()}, os.Args[1:]...)
 		rootCmd.SetArgs(args)
 	}
+	// command not known, i.e. happens for "bib quay.io/centos/..."
+	if err != nil && !slices.Contains([]string{"help", "completion"}, os.Args[1]) {
+		injectBuildArg()
+	}
+	// command appears valid, e.g. "bib --local quay.io/centos" but this
+	// is the parser just assuming "quay.io" is an argument for "--local" :(
+	if err == nil && cmd.Use == rootCmd.Use && cmd.Flags().Parse(os.Args[1:]) != pflag.ErrHelp {
+		injectBuildArg()
+	}
+
+	return rootCmd, nil
+}
+
+func run() error {
+	rootCmd, err := buildCobraCmdline()
+	if err != nil {
+		return err
+	}
 	return rootCmd.Execute()
 }
 

bib/cmd/bootc-image-builder/main_test.go

@@ -5,8 +5,11 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"testing"
 
+	"github.com/spf13/cobra"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -577,3 +580,69 @@ func TestBuildType(t *testing.T) {
 		})
 	}
 }
+
+func mockOsArgs(new []string) (restore func()) {
+	saved := os.Args
+	os.Args = append([]string{"argv0"}, new...)
+	return func() {
+		os.Args = saved
+	}
+}
+
+func addRunLog(rootCmd *cobra.Command, runeCall *string) {
+	for _, cmd := range rootCmd.Commands() {
+		cmd.RunE = func(cmd *cobra.Command, args []string) error {
+			callStr := fmt.Sprintf("<%v>: %v", cmd.Name(), strings.Join(args, ","))
+			if *runeCall != "" {
+				panic(fmt.Sprintf("runE called with %v but already called before: %v", callStr, *runeCall))
+			}
+			*runeCall = callStr
+			return nil
+		}
+	}
+}
+
+func TestCobraCmdline(t *testing.T) {
+	for _, tc := range []struct {
+		cmdline      []string
+		expectedCall string
+	}{
+		// trivial: cmd is given explicitly
+		{
+			[]string{"manifest", "quay.io..."},
+			"<manifest>: quay.io...",
+		},
+		{
+			[]string{"build", "quay.io..."},
+			"<build>: quay.io...",
+		},
+		{
+			[]string{"version", "quay.io..."},
+			"<version>: quay.io...",
+		},
+		// implicit: no cmd like build/manifest defaults to build
+		{
+			[]string{"--local", "quay.io..."},
+			"<build>: quay.io...",
+		},
+		{
+			[]string{"quay.io..."},
+			"<build>: quay.io...",
+		},
+	} {
+		var runeCall string
+
+		restore := mockOsArgs(tc.cmdline)
+		defer restore()
+
+		rootCmd, err := main.BuildCobraCmdline()
+		assert.NoError(t, err)
+		addRunLog(rootCmd, &runeCall)
+
+		t.Run(tc.expectedCall, func(t *testing.T) {
+			err = rootCmd.Execute()
+			assert.NoError(t, err)
+			assert.Equal(t, runeCall, tc.expectedCall)
+		})
+	}
+}