Optimization of concatenation steps
Concatenation is performed after the orthorectification. It consists in mixing (fusion) two images with the same date. It occurs when considering 2 SAFE images on the same orbit, same date (2 continous frames).
To avoid unnecessary writes on disk, it is desirable to avoid Calling concatenation application with a single input file.
In the case on a single image, the concatenation step consists in Moving the file from the tmp folder to the dataout folder. Doing a "move" rather a "copy" will improve the performance because there is no data block copy on the file system (if the filesystem is the same for tmp and dataout folders). So, the concatenation application must be called only when required (i.e. when 2 files has to be concatenated) and a "move" must be call when there is only a single file.