Default `cli.App.Usage` behaviour is very hard to override and leads to ugly help

My urfave/cli version is

v2.27.2

Checklist

[x] Are you running the latest v2 release? The list of releases is here.
[x] Did you check the manual for your release? The v2 manual is here (this is broken btw)
[x] Did you perform a search about this problem? Here's the GitHub guide about searching.

Dependency Management

My project is using go modules.

Describe the bug

This line of the code doesn't allow to set an empty cli.App.Usage value, which together with the fact that helpNameTemplate is not configurable makes it hard to have a clean HELP: section in the CLI docs. https://github.com/urfave/cli/blob/1210bdf785b2bddda680a262acc84d5e7b583460/command.go#L203

To reproduce

Create a cli.App{Usage: ""} or cli.App{} struct and launch it with --help.

Observed behavior

It's not possible to remove the "A new cli application" string from the help. Setting Usage to " " also leaves the -. The only way I've found is to entirely override cli.AppHelpTemplate or set Usage: "\b\b ".

Expected behavior

I would like to be able to set Usage to "" without it being overridden, or at least be able to customize helpNameTemplate to be able to remove the part that uses Usage.

Want to fix this yourself?

We'd love to have more contributors on this project! If the fix for this bug is easily explained and very small, feel free to create a pull request for it.

Run `go version` and paste its output here

go version go1.22.2 darwin/arm64

Run `go env` and paste its output here

GO111MODULE='auto'
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/redacted/Library/Caches/go-build'
GOENV='/Users/redacted/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/redacted/go/pkg/mod'
GOOS='darwin'
GOPATH='/Users/redacted/go'
GOROOT='/Users/redacted/sdk/go1.22.2'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/redacted/sdk/go1.22.2/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.22.2'
GCCGO='gccgo'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/redacted/cli_path/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/tp/x23ymr696x1fyzfy7rq7fr740000gp/T/go-build457189288=/tmp/go-build -gno-record-gcc-switches -fno-common'

urfave / cli