If you freeze your pip file, or even worse you run it in a container that depends on your requirements.txt the -e flag helps you to get:
-e git://github.com/ojii/pymaging.git@596a08fce5664e58d6e8c96847393fbe987783f2#egg=pymaging
-e git://github.com/ojii/pymaging-png.git@83d85c44e4b2342818e6c068065e031a9f81bb9f#egg=pymaging_png
If you freeze your pip file, or even worse you run it in a container that depends on your requirements.txt the -e flag helps you to get: -e git://github.com/ojii/pymaging.git@596a08fce5664e58d6e8c96847393fbe987783f2#egg=pymaging -e git://github.com/ojii/pymaging-png.git@83d85c44e4b2342818e6c068065e031a9f81bb9f#egg=pymaging_png
instead of the (normal looking, but failing)
pymaging==0.1 pymaging-png==0.1
which will fail terribly (see https://pip.readthedocs.io/en/stable/reference/pip_install/#git).