Merge commit '7563894' into v3-porting

docs/CHANGELOG.md

@@ -196,12 +196,12 @@ View [unreleased 1.22.X] series changes.
   there are no `ExitCoder`s in the `MultiError`.
 * Fixed YAML file loading on Windows (previously would fail validate the file path)
 * Subcommand `Usage`, `Description`, `ArgsUsage`, `OnUsageError` correctly
-  propogated
+  propagated
 * `ErrWriter` is now passed downwards through command structure to avoid the
   need to redefine it
 * Pass `Command` context into `OnUsageError` rather than parent context so that
-  all fields are avaiable
-* Errors occuring in `Before` funcs are no longer double printed
+  all fields are available
+* Errors occurring in `Before` funcs are no longer double printed
 * Use `UsageText` in the help templates for commands and subcommands if
   defined; otherwise build the usage as before (was previously ignoring this
   field)
@@ -225,7 +225,7 @@ View [unreleased 1.22.X] series changes.
   `CustomAppHelpTemplate`
 * Support for arbitrary key/value fields on `App` to be used with
   `CustomAppHelpTemplate` via `ExtraInfo`
-* `HelpFlag`, `VersionFlag`, and `BashCompletionFlag` changed to explictly be
+* `HelpFlag`, `VersionFlag`, and `BashCompletionFlag` changed to explicitly be
   `cli.Flag`s allowing for the use of custom flags satisfying the `cli.Flag`
   interface to be used.
 

docs/index.md

@@ -67,7 +67,7 @@ won't be able to call those. This reduces the resulting binary size by about
 ### Supported platforms
 
 cli is tested against multiple versions of Go on Linux, and against the latest
-released version of Go on OS X and Windows. This project uses Github Actions
+released version of Go on OS X and Windows. This project uses GitHub Actions
 for builds. To see our currently supported go versions and platforms, look at
 the [github workflow
 configuration](https://github.com/urfave/cli/blob/main/.github/workflows/cli.yml).

docs/v2/examples/flags.md

@@ -596,3 +596,53 @@ The precedence for flag value sources is as follows (highest to lowest):
 0. Environment variable (if specified)
 0. Configuration file (if specified)
 0. Default defined on the flag
+
+#### Flag Actions
+
+Handlers can be registered per flag which are triggered after a flag has been processed. 
+This can be used for a variety of purposes, one of which is flag validation
+
+<!-- {
+  "args": ["&#45;&#45;port","70000"],
+  "error": "Flag port value 70000 out of range[0-65535]"
+} -->
+```go
+package main
+
+import (
+	"log"
+	"os"
+	"fmt"
+
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	app := &cli.App{
+		Flags: []cli.Flag{
+			&cli.IntFlag{
+				Name:        "port",
+				Usage:       "Use a randomized port",
+				Value:       0,
+				DefaultText: "random",
+				Action: func(ctx *cli.Context, v int) error {
+					if v >= 65536 {
+						return fmt.Errorf("Flag port value %v out of range[0-65535]", v)
+					}
+					return nil
+				},
+			},
+		},
+	}
+
+	if err := app.Run(os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+Will result in help output like:
+
+```
+Flag port value 70000 out of range[0-65535]
+```