webfonts: fixes

[adrientetar]

• Treat WOFF as binary files so that git does not perform newline normalization.
• Replace corrupt Heuristica files with Source Serif Pro — italics are almost in production so I left Heuristica Italic which makes a good pair with SSP. Overall, Source Serif Pro is I think a better fit for rustdoc (cc @thehydroimpulse). This ought to fix "Heuristica" WOFF in documentation is corrupted #15527.
• Store Source Code Pro locally in order to make offline docs freestanding. Fixes Offline docs use webfonts #14778.

Preview: http://adrientetar.legtux.org/cached/rust-docs/core.html

r? @alexcrichton

[lilyball]

👍 on fixing the .gitattributes. Serving Source Code Pro locally is also probably a good idea for offline docs.

Not so sure about replacing Heuristica. I don't know what led to that font being chosen, but it seems like replacing that with Source Serif Pro should be an intentional decision and not something done purely because the Heuristica WOFF files are corrupt. Surely we can get non-corrupted Heuristica WOFF files?

That's not to say that using SSP is a bad idea. Perhaps it's a better fit, I don't know.

[adrientetar]

Surely we can get non-corrupted Heuristica WOFF files?

Of course, but there were a few negative opinions towards Heuristica during the original merge, then with the corrupt files and the fact that some people were willing to plain revert all rustdoc design changes there hasn't been a sheer discussion on the subject, through I expect that Source Serif Pro will be easier on the eye for that kind of use-case so I am proposing that unless people prefer Heuristica.
(Plus it's made by Adobe so we can expect top-notch support if any rendering problem was to arise.)

[alexcrichton]

To quote @brson from IRC:

12:03 <@acrichto> brson: do you know if we have to do anything about licensing for 
                  rustdoc to distribute fonts?
12:41 <@brson> acrichto: if our fonts use the SIL license then I beleive we can 
               basically distribute them w/o restriction

I'm not personally familiar with these fonts, but do you know what sort of license they come under?

[adrientetar]

• Fira Sans is under SIL
• Source Serif Pro is under SIL.
• Source Code Pro is under SIL.
• The remaining Heuristica weight is under SIL as well.

In fact, SIL OFL has been for long the de-facto standard for free and open-source fonts.

[adrientetar]

Original or Modified Versions of the Font Software may be bundled,
redistributed and/or sold with any software, provided that each copy
contains the above copyright notice and this license.

I'll add that.

[adrientetar]

@alexcrichton What I added in that last commit is basically four times the SIL modulo the different copyright statements. Is it fine to combine them together in one file?

[alexcrichton]

I'm not entirely sure, I would defer that question to @brson.

[mernen]

Since we're changing this line, wouldn't it be better if the fallback fonts were also serif? (Just "Source Serif Pro", serif would be enough, IMO)

[adrientetar]

Probably; I haven't tested default serifs on all major platforms just now through.