cmdline: move all postprocessing into command implementations

Drop the separate pre/postprocessed structs for install and download,
and the separate subcommand enum.

src/bin/rdcore/cmdline.rs

@@ -15,7 +15,6 @@
 // For consistency, have all parse_*() functions return Result.
 #![allow(clippy::unnecessary_wraps)]
 
-use anyhow::{bail, Result};
 use structopt::clap::AppSettings;
 use structopt::StructOpt;
 
@@ -96,25 +95,3 @@ pub struct StreamHashConfig {
     #[structopt(value_name = "hash-file")]
     pub hash_file: String,
 }
-
-/// Parse command-line arguments.
-pub fn parse_args() -> Result<Cmd> {
-    let config = Cmd::from_args();
-    if let Cmd::Kargs(ref config) = config {
-        check_kargs(config)?;
-    }
-    Ok(config)
-}
-
-fn check_kargs(config: &KargsConfig) -> Result<()> {
-    // we could enforce these via clap's ArgGroup, but I don't like how the --help text looks
-    if !(config.boot_device.is_some()
-        || config.boot_mount.is_some()
-        || config.current
-        || config.override_options.is_some())
-    {
-        // --override-options is undocumented on purpose
-        bail!("one of --boot-device, --boot-mount, or --current required");
-    }
-    Ok(())
-}

src/bin/rdcore/kargs.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use anyhow::{Context, Result};
+use anyhow::{bail, Context, Result};
 use std::fs::read_to_string;
 
 use libcoreinst::install::*;
@@ -23,6 +23,16 @@ use crate::cmdline::*;
 use crate::rootmap::get_boot_mount_from_cmdline_args;
 
 pub fn kargs(config: &KargsConfig) -> Result<()> {
+    // we could enforce these via clap's ArgGroup, but I don't like how the --help text looks
+    if !(config.boot_device.is_some()
+        || config.boot_mount.is_some()
+        || config.current
+        || config.override_options.is_some())
+    {
+        // --override-options is undocumented on purpose
+        bail!("one of --boot-device, --boot-mount, or --current required");
+    }
+
     if let Some(ref orig_options) = config.override_options {
         modify_and_print(config, orig_options.trim()).context("modifying options")?;
     } else if config.current {

src/bin/rdcore/main.rs

@@ -17,14 +17,13 @@ mod kargs;
 mod rootmap;
 mod stream_hash;
 
-use anyhow::{Context, Result};
+use anyhow::Result;
+use structopt::StructOpt;
 
 use crate::cmdline::*;
 
 fn main() -> Result<()> {
-    let config = cmdline::parse_args().context("parsing arguments")?;
-
-    match config {
+    match Cmd::from_args() {
         Cmd::Kargs(c) => kargs::kargs(&c),
         Cmd::Rootmap(c) => rootmap::rootmap(&c),
         Cmd::StreamHash(c) => stream_hash::stream_hash(&c),