I'd been hoping we could avoid it and let the rest of the internet handle advanced git advice, but based on conversations in #6254, it seems like a troubleshooting / advanced git page might be wanted (at least by some)?

• when, how, and why to rebase
• tips like git push -u
• git commit --amend and git push --force
• git stash
• git diff
• discussion of git GUIs

Other advanced dev topics:

• PR best practices (e.g., linking to changed doc pages on Circle after they render, when to add tests / changelog entries, etc)
• overview of our CIs (memory limits, what gets tested where, etc)
• figuring out why CircleCI / Azure / Travis errorred
• reviewing PRs, making "suggestions", committing "suggestions" through the web UI...
• profiling: link to sklearn profiling page
• docstring formatting guidelines (e.g., where we deviate from the NumPyDoc style)

@jeythekey @massich @larsoner @mmagnuski