remove duplicate code in validation

[marcoieni]

I extracted a variable.

AI disclosure

I used GPT5.6-Sol with the codex harness to generate this change. I reviewed its output and changed it where necessary.

[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Team Diffs:
    ➕ Creating team:
      Org: rust-lang
      Name: rust-timer
      Description: Managed by the rust-lang/team repository.
      Privacy: closed
      Members:
        rust-timer: member

[Kobzol]

Cloning iterators is a bit icky, I usually create a closure instead (let alumni = || ...) and then call it repeatedly.

[steffahn]

Alternatively, to reduce some of the duplication already, the "leads + alumni" check isn't really necessary in the first place, given that we also check leads is a subset of members.

[steffahn]

Also actually, with the "members + alumni" check in place, the individual checks on members and on alumni become redundant, because those also create duplicates in members + alumni combined

[steffahn]

so you just need 2 checks total; one on members + alumni and one on leads. And no duplicate code is left at all

[Kobzol]

Yeah, but this situation is so rare that I didn't want to bother with it. And if we only check members + alumni together, then the error message will be misleading (it would have to be generalized to something like "there is duplication either amongst members or members + alumni").

[steffahn]

This is what I thought it can look like: #2702

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[marcoieni]

Thanks both!
I implemented Kobzol's suggestion. I'll let the reviewer decide which approach they prefer. If they prefer #2702, feel free to close this PR. 👍