CONTRIBUTING.md: `pretty.fixes` git config is confusing

[dseomn]

This section of CONTRIBUTING.md looks like it's mixing two separate things, the way to reference a bug that will be fixed by a commit, and the way to reference a commit:

https://github.com/containers/common/blob/954a8ceee5a2bc04f7033a67b26e23279f89f77b/CONTRIBUTING.md?plain=1#L163-L166

Is there any reason to use a git pretty format for Fixes:?

Using a config like that does make sense for referencing a commit. There is a very similar format already built into git though, --pretty=reference:

$ git show --pretty=reference --abbrev=12 --no-patch ebbd38fd7111a0299c30234dc6d0fcb9329a69f6
ebbd38fd7111 (ci: switch to golangci-lint v2.0, 2025-03-25)