fix: Improve error handling for Contents API response

Ensure response body is properly closed even when an error occurs by moving
the defer statement before the error check. This prevents potential resource
leaks when the Contents API returns an error with a non-nil response.

Changes:
- Move defer respContents.Body.Close() before error checking
- Rename errContents to err for consistency
- Add nil check for respContents before attempting to close body

This follows Go best practices for handling HTTP responses and prevents
potential goroutine/memory leaks.

Author: yonaka15

pkg/github/repositories.go

@@ -510,11 +510,13 @@ func GetFileContents(getClient GetClientFn, getRawClient raw.GetRawClientFn, t t
 				// First, get file info from Contents API to retrieve SHA
 				var fileSHA string
 				opts := &github.RepositoryContentGetOptions{Ref: ref}
-				fileContent, _, respContents, errContents := client.Repositories.GetContents(ctx, owner, repo, path, opts)
-				if errContents == nil && respContents.StatusCode == http.StatusOK && fileContent != nil && fileContent.SHA != nil {
-					fileSHA = *fileContent.SHA
+				fileContent, _, respContents, err := client.Repositories.GetContents(ctx, owner, repo, path, opts)
+				if respContents != nil {
 					defer func() { _ = respContents.Body.Close() }()
 				}
+				if err == nil && respContents.StatusCode == http.StatusOK && fileContent != nil && fileContent.SHA != nil {
+					fileSHA = *fileContent.SHA
+				}
 
 				rawClient, err := getRawClient(ctx)
 				if err != nil {