Looking at that code I’m shocked that Postgres allows two-liner if statements without a matching {} (I’m sure someone pedantically will point out that I’m using the wrong terminology or that it was actually several lines of conditionals).
This practice is very bug prone, and has lead to high profile failures like goto fail
The project history goes back to 1982. There may have been rewrites in the later 80s, but it's some of the oldest C around, and a very conservative codebase (e.g. Linux kernel gets much more aggressive refactorings regularly).
These days people might not blink an eye at gofmt/rustfmt rewriting the AST to clean it up, but those toolchains were built that way largley because automating anything about large C codebases is so hard.
Large stable projects are very much wary of wide-scale changes their codebase. What they have is tested working by decades in production. Especially with C where tooling is brittle.
Let me put this way: If you submit a code prettifying patch to the Linux kernel, it will not be accepted. The risks aren't worth it.
The only real way forward is full migration away from C, for which a better scope is a separate project.
These days, there are compiler diagnostics for that. There's also a pgindent tool, which will align the visual presentation of the code with its syntactic structure.
Are you saying they should always be present? Or only when the condition takes multiple lines; i.e. do you take issue with the ifs in zone_name_pref too?
Personally I think the indentation does a good enough job here.
This practice is very bug prone, and has lead to high profile failures like goto fail