refactor: centralize GitHub token retrieval logic into utility function

## CHANGES

- Extract token retrieval into `util.GetTokenFromEnv` function
- Support both `GITHUB_TOKEN` and `GH_TOKEN` environment variables
- Replace direct `os.Getenv` calls with utility function
- Add new `util/token.go` file for token handling
- Update walker.go to use centralized token logic
- Update main.go to use token utility function

cmd/generate_changelog/internal/git/walker.go

@@ -2,12 +2,12 @@ package git
 
 import (
 	"fmt"
-	"os"
 	"regexp"
 	"strconv"
 	"strings"
 	"time"
 
+	"github.com/danielmiessler/fabric/cmd/generate_changelog/util"
 	"github.com/go-git/go-git/v5"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/object"
@@ -520,7 +520,7 @@ func (w *Walker) PushToRemote() error {
 	pushOptions := &git.PushOptions{}
 
 	// Check if we have a GitHub token for authentication
-	if githubToken := os.Getenv("GITHUB_TOKEN"); githubToken != "" {
+	if githubToken := util.GetTokenFromEnv(""); githubToken != "" {
 		// Get remote URL to check if it's a GitHub repository
 		remotes, err := w.repo.Remotes()
 		if err == nil && len(remotes) > 0 {

cmd/generate_changelog/main.go

@@ -5,9 +5,10 @@ import (
 	"os"
 	"path/filepath"
 
-	internal "github.com/danielmiessler/fabric/cmd/generate_changelog/internal"
+	"github.com/danielmiessler/fabric/cmd/generate_changelog/internal"
 	"github.com/danielmiessler/fabric/cmd/generate_changelog/internal/changelog"
 	"github.com/danielmiessler/fabric/cmd/generate_changelog/internal/config"
+	"github.com/danielmiessler/fabric/cmd/generate_changelog/util"
 	"github.com/joho/godotenv"
 	"github.com/spf13/cobra"
 )
@@ -55,9 +56,7 @@ func run(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("--release cannot be used with other processing flags")
 	}
 
-	if cfg.GitHubToken == "" {
-		cfg.GitHubToken = os.Getenv("GITHUB_TOKEN")
-	}
+	cfg.GitHubToken = util.GetTokenFromEnv(cfg.GitHubToken)
 
 	generator, err := changelog.New(cfg)
 	if err != nil {

cmd/generate_changelog/util/token.go

@@ -0,0 +1,15 @@
+package util
+
+import (
+	"os"
+)
+
+func GetTokenFromEnv(tokenValue string) string {
+	if tokenValue == "" {
+		tokenValue = os.Getenv("GITHUB_TOKEN")
+		if tokenValue == "" {
+			tokenValue = os.Getenv("GH_TOKEN")
+		}
+	}
+	return tokenValue
+}