upgrade: list upgradeable dependencies on dry run

[EricFromCanada]

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Currently, a dry run of brew upgrade only lists which dependents of the given packages will be auto-upgraded. This adds a list of dependencies to be auto-upgraded to the output.

Before:

$ brew upgrade -n nghttp2 harfbuzz
==> Would upgrade 2 outdated packages:
nghttp2 1.43.0 -> 1.44.0
harfbuzz 2.8.1 -> 2.9.0
==> Would upgrade 4 dependents:
unbound 1.13.1 -> 1.13.2, gnupg 2.3.1_1 -> 2.3.2, pango 1.48.5 -> 1.48.9, gtk+3 3.24.29 -> 3.24.30
==> No currently broken dependents found!
Warning: If they are broken by the upgrade they will also be upgraded or reinstalled.

After:

$ brew upgrade -n nghttp2 harfbuzz
==> Would upgrade 2 outdated packages:
nghttp2 1.43.0 -> 1.44.0
harfbuzz 2.8.1 -> 2.9.0
==> Would upgrade 3 dependencies for nghttp2:
openssl@1.1 1.1.1k -> 1.1.1l, cmake 3.21.1 -> 3.21.2, c-ares 1.17.1 -> 1.17.2
==> Would upgrade 4 dependencies for harfbuzz:
openssl@1.1 1.1.1k -> 1.1.1l, meson 0.59.0 -> 0.59.1, freetype 2.10.4 -> 2.11.0, glib 2.68.3 -> 2.68.4
==> Would upgrade 4 dependents:
unbound 1.13.1 -> 1.13.2, gnupg 2.3.1_1 -> 2.3.2, pango 1.48.5 -> 1.48.9, gtk+3 3.24.29 -> 3.24.30
==> No currently broken dependents found!
Warning: If they are broken by the upgrade they will also be upgraded or reinstalled.

[BrewTestBot]

Review period will end on 2021-08-31 at 23:23:12 UTC.

[MikeMcQuaid]

Makes sense to me! Some suggested improvements but can be in a follow-up PR.

[EricFromCanada]

Added dry run modes to migration and cleanup steps:

$ brew upgrade -n nghttp2 harfbuzz
==> Would upgrade 2 outdated packages:
nghttp2a 1.44.0
harfbuzz 2.8.1 -> 2.9.0
==> Would migrate nghttp2 to nghttp2a
==> Would upgrade 3 dependencies for nghttp2a:
openssl@1.1 1.1.1k -> 1.1.1l, cmake 3.21.1 -> 3.21.2, c-ares 1.17.1 -> 1.17.2
==> Would run `brew cleanup` which has not been run in the last 30 days
==> Would upgrade 4 dependencies for harfbuzz:
openssl@1.1 1.1.1k -> 1.1.1l, meson 0.59.0 -> 0.59.1, freetype 2.10.4 -> 2.11.0, glib 2.68.3 -> 2.68.4
==> Would run `brew cleanup` which has not been run in the last 30 days
==> Would upgrade 4 dependents:
unbound 1.13.1 -> 1.13.2, gnupg 2.3.1_1 -> 2.3.2, pango 1.48.5 -> 1.48.9, gtk+3 3.24.29 -> 3.24.30
==> No currently broken dependents found!
Warning: If they are broken by the upgrade they will also be upgraded or reinstalled.

Also added a dry run mode to migrate:

$ brew migrate -n nghttp2
==> Would migrate nghttp2 to nghttp2a

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Great work as usual @EricFromCanada!