functional flag builder pattern

[acheong08]

I've noticed that some flags aren't exposed by the cli/root command and that every time a new flag type is added, you have to wrap it.

clir/command.go

Lines 820 to 831 in 9a039b7

	func (c *Command) Float64Flag(name, description string, variable *float64) *Command {
	c.flags.Float64Var(variable, name, *variable, description)
	c.flagCount++
	return c
	}
	// Float32Flag - Adds a float32 flag to the command
	func (c *Command) Float32Flag(name, description string, variable *float32) *Command {
	c.flags.Var(newFloat32Value(*variable, variable), name, description)
	c.flagCount++
	return c
	}

clir/cli.go

Lines 115 to 125 in 9a039b7

	// BoolFlag - Adds a boolean flag to the root command.
	func (c *Cli) BoolFlag(name, description string, variable *bool) *Cli {
	c.rootCommand.BoolFlag(name, description, variable)
	return c
	}
	// StringFlag - Adds a string flag to the root command.
	func (c *Cli) StringFlag(name, description string, variable *string) *Cli {
	c.rootCommand.StringFlag(name, description, variable)
	return c
	}

Using the functional paradigm, we can simplify to this:

cli.WithFlags(
  clir.BoolFlag("name", "desc", &boolVar),
  clir.Float64Flag("lorum", "ipsum", &floatVar),
  ...
)

All the flag code is thus shared and you just have this in cli/command

diff --git a/cli.go b/cli.go
index 47a0849..ffc475c 100644
--- a/cli.go
+++ b/cli.go
@@ -112,6 +112,13 @@ func (c *Cli) PostRun(callback func(*Cli) error) {
    c.postRunCommand = callback
 }
 
+func (c *Cli) WithFlags(flags ...flagFunc) *Cli {
+   for _, f := range flags {
+       f(c.rootCommand)
+   }
+   return c
+}
+

diff --git a/command.go b/command.go
index 5ac8754..4a1282e 100644
--- a/command.go
+++ b/command.go
 
+func (c *Command) WithFlags(flags ...flagFunc) *Command {
+   for _, f := range flags {
+       f(c)
+   }
+   return c
+}
+