docs(cli): update usage sections, cmd descriptions

 - updated README getting started section to work with new cobra CLI
 - updated subcommand use section, short descriptions and long
   descriptions to provide more information
    - particularly, they now show the positional arguments in "Usage"
    - added descriptions of the positional arguments in the long description
    - these are kind of inelegant, see these issues in cobra for why
      this had to be done
        - spf13/cobra#395
        - spf13/cobra#378

README.md

@@ -15,22 +15,23 @@ go install github.com/Samyak2/guntainer@latest
 ```
 (ensure `GOBIN` is in path)
 
-To run a container:
+
+Confirm that the installation succeeded.
 ```
-guntainer run <archive_of_root_FS> <command_to_run> <args_for_command>...
+guntainer help
 ```
 
- - `archive_of_root_FS` is an archive (tar, zip, etc.) of a root filesystem which will be `chroot`ed into
- - `command_to_run` is a program *inside* the container root FS that is run (note that `PATH` is not set unless you execute a shell)
- - `args_for_command` are arguments for the program (everything after the `command_to_run` is passed directly to the program)
-
-
-To build a new image, first make a [`Gunfile`](#building-images) and then use:
+To run a container image, use the `run` subcommand.
+See [here](#run-examples) for more information and examples.
 ```
-guntainer build Gunfile <path_to_new_image>
+guntainer run --help
 ```
 
-Where `Gunfile` can be replaced with the path to the Gunfile and `path_to_new_image` is the path where the generated image is saved (as a tar file)
+To build a container image using a `Gunfile`, use the `build` subcommand.
+See [here](#building-images) for more information and examples.
+```
+guntainer build --help
+```
 
 ## Building images
 
@@ -45,7 +46,7 @@ More examples can be found [here](./examples/).
 
 To build the image from [example_02](./examples/02_alpine_vim/), we can use:
 ```
-guntainer build examples/02_alpine_vim/Gunfile example_02.tar
+guntainer build example_02.tar examples/02_alpine_vim/Gunfile
 ```
 
 This will generate an `example_02.tar` which is the newly built image with `vim` installed. Run it using:

cmd/build.go

@@ -6,11 +6,16 @@ import (
 )
 
 var buildCommand = &cobra.Command{
-	Use:   "build",
+	Use:   "build [image-path] (Gunfile-path)",
 	Short: "Build a new container from a Gunfile",
-	Long:  "Executes the Gunfile to build a new container image.",
+	Long:  `Executes the Gunfile to build a new container image.
+
+ image-path:	is where the resulting container image will be saved.
+ Gunfile-path:	(optional) is the path to the Gunfile to use for building the image.`,
+	DisableFlagsInUseLine: true,
+
 	Args: cobra.RangeArgs(1, 2),
-	Run: func(cmd *cobra.Command, args []string) {
+	Run: func(_ *cobra.Command, args []string) {
 		if len(args) > 1 {
 			core.Build(args[1], args[0])
 		} else {

cmd/run.go

@@ -6,11 +6,18 @@ import (
 )
 
 var runCmd = &cobra.Command{
-	Use:   "run",
+	Use:   "run [image-path] [command]",
 	Short: "Run an existing container",
-	Long:  "Run the archive of root FS as a container.",
+	Long:  `Run the archive of root FS as a container.
+
+ image-path:	 is an archive (tar, zip, etc.) of a root filesystem which will be 'chroot'ed into.
+ command:	is a program *inside* the container root FS that is run (note that PATH is not set unless you execute a shell).
+
+Everything after the 'command' is passed as arguments directly to the command inside the container.`,
+	DisableFlagsInUseLine: true,
+
 	Args: cobra.MinimumNArgs(2),
-	Run: func(cmd *cobra.Command, args []string) {
+	Run: func(_ *cobra.Command, args []string) {
 		core.Run(args[0], args[1], args[2:])
 	},
 }