Adhere to provider-specific limits.

[RokeJulianLockhart]

A broader scope of #650 (comment). As two examples:

1. GitHub solely permits 100 commits per push.

2. GitLab solely permits 100 MiB per commit.

   This occurs to me when trying to maintain Minecraft modpacks with multiple large .jars.

Modifying pushes (upon acceptance to a prompt) would be incredibly useful, because us users wouldn't need to manually tailor our commits and pushes for the provider we are using.