Modifying upstream crates

[jethrogb]

Inevitably, you'll come across a crate which requires minor patches to be
compatible with another platform. Currently there are two options to deal with
this situation:

1. Send patches adding platform support upstream
2. Require downstream users of your create to use your fork

This issue proposes finding a middle ground between these options in case
upstream is not cooperating.

[Ericson2314]

I'm not sure there exists such a good middle ground, but it would be cool to be wrong! As it stands, I think our goal should be to make the situation good enough that there's no reason that upstream wouldn't take the patch. [patch] in Cargo ought to work well enough that the second case isn't so bad until they do.

[jethrogb]

One (probably bad) idea I had is to allow [patch] statements to trickle up the dependency tree.

[Ericson2314]

What do you mean by that?

[jethrogb]

I guess I hadn't really thought it through. Maybe better is if you could specify [patch] sections per target in your cargo config?

[pierzchalski]

The alternative being to do some target-specific [cfg]s in your patched version?

[jethrogb]

Related rust-lang/rfcs#2624