`HOMEBREW_CURL_PATH` has an effect only when `HOMEBREW_DEVELOPER` is set. However, the part of `brew.sh` that prints a message about outdated cURL disregards the value of `HOMEBREW_DEVELOPER`, which leads to a misleadnig message telling the user that `HOMEBREW_CURL_PATH` is outdated even though another cURL was used/tested.
This PR fixes it and instructs Homebrew to:
1. Display a warning message when system cURL is outdated and either `HOMEBREW_CURL_PATH` **or `HOMEBREW_DEVELOPER`** are not set. New `HOMEBREW_CURL_WARNING` variable is set to display the above warning only once (useful when `brew` calls itself internally).
2. Display `Installing Homebrew cURL` before auto-installing cURL in `update.sh` (due to `HOMEBREW_FORCE_BREWED_CURL`) and stop/exit if this step fails.
3. Display `Installing Homebrew Git` before auto-installing Git in `update.sh` (due to `HOMEBREW_FORCE_BREWED_GIT`) and stop/exit if this step fails.
- Ordering them this way seems to require less `--fix`ing in
Homebrew/homebrew-core than the other way around.
- In the Big Sur bottling, we found many repos that were archived. We've
been going through and deprecating repos that are archived or that
don't build any more. I felt weird without the ordering of these
stanzas without an audit to guide me - I spent time looking at
previous examples to see "should `deprecate!` go before or after
`depends_on`" question. Computers can tell us this instead.
- Suppress (some more) warnings when doing `brew install --quiet`
- Clarify `man brew` output that we don't suppress all warnings
for all commands with `--quiet`
While I was doing this I noticed references to the (soon to be
deprecated) `brew switch` so:
- remove these references in `install` output
- remove a reference in the documentation
- add a comment to remind me to deprecate `brew diy`, too
Fixes#9179
