upgrade: print the fetch heading before prefetching

[bevanjkay]

Alternative to #23638.

• Print the ==> Fetching downloads for: heading immediately after the upgrade prompt, using the names the ask preview has already worked out, so confirming with y prints something straight away rather than after the prefetch that currently supplies them.
• Extract the print_heading logic to a method so we can call it from the other site.
• Skip the heading in fetch when it has already been printed, leaving the non-ask path and its Fetching dependency downloads fallback unchanged.
• Two drawbacks with this implentation: the heading now names what the preview planned, so a package filtered out during prefetch can be named in a heading it isn't fetched under, and ==> Downloading bottle manifests now outputs under the heading rather than preceding it.

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• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

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I used claude-code with Opus 5, to implement the change.

[MikeMcQuaid]

Thanks, much nicer!

[Copilot]

Pull request overview

This PR adjusts brew upgrade’s interactive (ask) flow to print the “Fetching downloads for:” heading immediately after the user confirms the prompt, rather than waiting until after prefetch has determined download names. It does this by extracting heading printing into Homebrew::DownloadQueue and reusing it earlier in the upgrade command.

Changes:

• Add Homebrew::DownloadQueue#print_heading and reuse it from DownloadQueue#fetch.
• In brew upgrade, print the combined fetch heading before prefetching when running the shared download queue path.
• Update/extend upgrade command specs to account for the new print_heading call and assert ordering.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Library/Homebrew/cmd/upgrade.rb	Prints the combined “Fetching downloads for:” heading earlier in the interactive upgrade path and avoids re-printing it later.
Library/Homebrew/download_queue.rb	Extracts heading emission into print_heading and reuses it in fetch.
Library/Homebrew/test/cmd/upgrade_spec.rb	Updates DownloadQueue doubles for the new API and adds a spec asserting heading-before-prefetch behavior.

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