Fix broken "special type formatter" \fT \fE \fM when running gallery-dl in Linux

[Tobi823]

I want to use the "Special Type Format Strings" but gallery-dl completely ignores these formatters.

It seems that \f in the parameter --filename is converted to \\f.

By calling gallery-dl -f "\fM test20220313:generate_text" https://some.web.site, the argument format_string in formatter.py:parse is set to \\fM test20220313:generate_text. This breaks the detection and extraction of the special type formatters.

This pull request is a quick fix for this problem. Feel free to improve it.

[Tobi823]

(This is an older screenshot. I later replaced the kind[2:] with kind[-1])

[mikf]

The problem seems to be that bash doesn't interpret \f as form feed character (ASCII code 12 or 0xC). To type it in bash, hold Ctrl and press v followed by l and you will get something that looks like ^L, but it's actually just one character, not ^ + L.

JSON has no problem with \f, that's a bash issue.

[Tobi823]

Using the Unicode character 'FORM FEED (FF)' aka \f is in my opinion a very odd choice. I did not expect that. The documentation should highlight this (see #2406).

And I found a workaround for the Linux Bash:

• Print the format string with printf.
• Printf will convert \f to the form feed character.
• Pass the output to gallery-dl

This works for me: gallery-dl -f "$(printf '\fM my_module:generate_file_name')"

[Tobi823]

Here is my new pull-request (#2406)

Feel free to close this pull-request and merge my new one.

In my place I would have changed the code, but improving the documentation is good enough (to prevent this beginners trap).