rustdoc: Tracking issue for command-line flag `--no-capture`

[fmease]

A command line option to prevent rustdoc from capturing the stdout/stderr output from doctests.

Note

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Steps

• Implementation PR
• Stabilization PR

Unresolved questions

• Should we reject --no-capture if --test wasn't passed? Note that we don't so for similar flags (e.g., --test-args), so it's probably moot. We could/should however at least warn in such cases.
• If we rename --nocapture to --no-capture (rustdoc: Rename unstable option --nocapture to --no-capture in accordance with libtest #148115), should we keep around the old version for a while in a soft-deprecated then hard-deprecated state?
• I think the original intention was to update Cargo to use this flag instead of --test-args --no-capture / --test-args --nocapture. However the relevant PR was closed (Rustdoc nocapture cargo#9705). How should we proceed?

Implementation history

• Add --nocapture option to rustdoc #86230
• rustdoc: Rename unstable option --nocapture to --no-capture in accordance with libtest #148115