anonymize homedirs in generated docs (#14101)

Signed-off-by: Andrew Mason <andrew@planetscale.com>

go/cmd/internal/docgen/docgen.go

@@ -49,6 +49,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/cobra/doc"
@@ -84,6 +85,10 @@ func GenerateMarkdownTree(cmd *cobra.Command, dir string) error {
 		return fmt.Errorf("failed to index doc (generated at %s) into proper position (%s): %w", rootDocPath, indexDocPath, err)
 	}
 
+	if err := anonymizeHomedir(indexDocPath); err != nil {
+		return fmt.Errorf("failed to anonymize homedir in help text for command %s: %w", indexDocPath, err)
+	}
+
 	if err := restructure(dir, dir, cmd.Name(), cmd.Commands()); err != nil {
 		return err
 	}
@@ -123,10 +128,15 @@ func restructure(rootDir string, dir string, name string, commands []*cobra.Comm
 				return fmt.Errorf("failed to create subdir for %s: %w", fullCmdFilename, err)
 			}
 
-			if err := os.Rename(filepath.Join(rootDir, fullCmdFilename+".md"), filepath.Join(cmdDir, "_index.md")); err != nil {
+			indexFile := filepath.Join(cmdDir, "_index.md")
+			if err := os.Rename(filepath.Join(rootDir, fullCmdFilename+".md"), indexFile); err != nil {
 				return fmt.Errorf("failed to move index doc for command %s with children: %w", fullCmdFilename, err)
 			}
 
+			if err := anonymizeHomedir(indexFile); err != nil {
+				return fmt.Errorf("failed to anonymize homedir in help text for command %s: %w", indexFile, err)
+			}
+
 			if err := restructure(rootDir, cmdDir, fullCmdFilename, children); err != nil {
 				return fmt.Errorf("failed to restructure child commands for %s: %w", fullCmdFilename, err)
 			}
@@ -150,6 +160,10 @@ func restructure(rootDir string, dir string, name string, commands []*cobra.Comm
 			if out, err := sed.CombinedOutput(); err != nil {
 				return fmt.Errorf("failed to rewrite links to parent command in child %s: %w (extra: %s)", newName, err, out)
 			}
+
+			if err := anonymizeHomedir(newName); err != nil {
+				return fmt.Errorf("failed to anonymize homedir in help text for command %s: %w", newName, err)
+			}
 		default:
 			// Top-level command without children. Nothing to restructure.
 			continue
@@ -163,6 +177,31 @@ func newParentLinkSedCommand(parent string, file string) *exec.Cmd {
 	return exec.Command("sed", "-i", "", "-e", fmt.Sprintf("s:(./%s/):(../):i", parent), file)
 }
 
+var (
+	wd   string
+	once sync.Once
+)
+
+func anonymizeHomedir(file string) (err error) {
+	once.Do(func() {
+		// Only do this once per run.
+		wd, err = os.Getwd()
+	})
+	if err != nil {
+		return err
+	}
+
+	// We're replacing the stuff inside the square brackets in the example sed
+	// below:
+	// 	's:Paths to search for config files in. (default \[.*\])$:Paths to search for config files in. (default \[$WORKDIR\]):'
+	sed := exec.Command("sed", "-i", "", "-e", fmt.Sprintf("s:%s:$WORKDIR:i", wd), file)
+	if out, err := sed.CombinedOutput(); err != nil {
+		return fmt.Errorf("%w: %s", err, out)
+	}
+
+	return nil
+}
+
 func recursivelyDisableAutoGenTags(root *cobra.Command) {
 	commands := []*cobra.Command{root}
 	for cmd := commands[0]; len(commands) > 0; cmd, commands = commands[0], commands[1:] {