Make `git format-patch` preferred way of generating patches.

[delphij]

Summary

git format-patch would generate patchsets that can be applied with
git am and preserve author identity like name and email.

[imp]

Looks good to me. My preferred workflow is a little different, but there's nothing at all wrong with this one.

[emaste]

I might get rid of the git diff > xxx altogether - if the submitter is using git I think we can insist on a git format-patch. The diff -u advice where the submitter is not using git makes sense.

documentation/content/en/articles/problem-reports/_index.adoc

174–180

In general is maybe more typical phrasing?