[vidigoat]

What type of PR is this?

• bug

What this PR does / why we need it:

#2475 cut command and flag usage to its first line in the --generate-shell-completion output, because the completion scripts read one suggestion per line. The static script from ToFishCompletion still writes the whole usage into -d '...':

Flags:    []cli.Flag{&cli.StringFlag{Name: "out", Usage: "write to FILE\nor - for stdout"}},
Commands: []*cli.Command{{Name: "build", Usage: "build the project\nand all its dependencies"}},

complete -c app -n '__fish_app_no_subcommand' -f -l out -r -d 'write to FILE
or - for stdout'

With that script sourced in fish 4.9.3, complete -C "app " prints the second line on its own:

build	build the project
and all its dependencies
test	run tests

and complete -C "app --" does the same with or - for stdout. fish.go now uses completionUsage from #2475 for both the command and the flag descriptions, so the output is build build the project. A usage that starts with a newline gets no -d instead of an empty one. Help output still shows the full usage.

Which issue(s) this PR fixes:

None, found while testing the completion scripts in fish. It is the static-script half of #2475.

Testing

• New TestFishCompletionUsesFirstLineOfUsage covers \n, \r\n and a usage starting with a newline. It fails on main.
• The fish part of testdata/expected-help-output.txt now has one-line descriptions for the three multi-line usages it already had (--log, delete and set-a-very-long-name); nothing else in the golden file changes.
• Checked the generated script in fish 4.9.3 as above.
• make (generate, vet, tests, binary size, gfmrun), make lint and make v3diff pass. go test -race passes, as do the tests with urfave_cli_no_template, urfave_cli_no_docs and urfave_cli_no_suggest.

The change and the tests were written with Claude Code (AI).

Release Notes

The fish completion script from ToFishCompletion now uses only the first line of a multi-line Usage as the description, like the other completion output.

🤖 Generated with Claude Code