samtools merge single file too slow. #2145
Description
The samtools merge command is capable of merging any number of BAM files, including a single file for compatibility purposes. However, when provided with only one file, the merge operation still takes an unnecessarily long time. This issue could be addressed by adding a pre-check in the command logic. Ideally, though, it would be more efficient if samtools merge could automatically detect and handle single-file input without performing a full merge operation.