alias: abort on missing positional args (issue3331)

phases: fix a non-standard debug message - add missing newline - ditch gratuitous use of string formatting with dict - fix so it actually does string formatting ('%' rather than ',') - inline unnecessary local variable - downcase first word

convert/git: abort if git submodules are detected (issue2150) This improves the error message when convert encounters a git submodule. Now, instead of a git-cat-file error, we'll directly report the lack of support for git submodules.