Add overwrite flag

[gtuk]

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[gtuk]

I signed it!

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[romainmenke]

You can already achieve this behaviour by pointing the input and output args to the same file. IMHO adding this flag increases complexity of the cli without improving it.

[gtuk]

You mean something like "guetzli beens.png" should automaticly create a compressed file called beens.jpg if there is not output file given?

[mgrhm]

I disagree with @romainmenke on this one. Adding an overwrite flag does improve the program and its CLI, at the cost of only a small increase in complexity. It doesn't break default behaviour since it needs to be explicitly called. It's ideal for situations where a user wants to compress an existing JPG file without ending up with a second copy of the same image.

[romainmenke]

@gtuk Try guetzli ./my_image.jpeg ./my_image.jpeg. Unless I am mistaken it will replace the original file with the output.

guetzli ./my_image.jpeg ./my_image.jpeg
vs
guetzli --overwrite ./my_image.jpeg

So this adds extra code that has to be maintained without adding functionality.

Such a flag would make sense in a program that does batch compressions and alters filenames to prevent overwrites. Since Guetzli does neither I personally don't really see the added value.