Feature request: Command-line options

[JaapJoris]

It would be nice to have some more control over DJHTML's behavior through command-line arguments. @sjoerdjob suggested the following options:

• --check to only check files and not alter their contents
• --diff to show the diff between the input file and the would-be output file
• support for multiple files as arguments
• support for directory names as arguments

[sjoerdjob]

While working on this, it would probably also be good to not overwrite the file when nothing has changed.

Would you prefer to use a dependency like Click for command-line parsing, or is optargs/argparse good enough, with the benefit of no dependencies?

[JaapJoris]

argparse will do fine. Let's try to keep DJHTML as dependency-free as possible. Although I have to admit I'm mouthwatering at pytidylib...