v3.9.1

What's Changed

• fix: inherit Reader/Writer/ErrWriter from parent on subcommand setup by @c-tonneslan in #2329
• fix: correct greedy colon parsing in bash completion script by @TimSoethout in #2336
• fix: Honor env sources on duplicated flags by @ibobgunardi in #2355
• fix: Remove incorrect flag check by @MohitPanchariya in #2280
• fix: let completion command use normal flag parsing pipeline by @suzuki-shunsuke in #2279
• fix: bash completion spacing by @cyphercodes in #2337
• fix: fish custom completion arguments by @puneetdixit200 in #2338
• fix: empty positional arg after a flag regression test by @c-tonneslan in #2328
• docs: document build tags in v3 migration guide by @dearchap in #2358
• chore(deps): bump mkdocs-git-revision-date-localized-plugin by @dependabot in #2347
• Fix typos by @myfloss in #2339

Full Changelog: v3.9.0...v3.9.1