Fix for when only verbosity flags are passed

Author: Xion

src/args.rs

@@ -120,8 +120,8 @@ pub struct Options {
     pub locality: Option<Locality>,
     /// Gist command that's been issued.
     pub command: Command,
-    /// Gist to operate on.
-    pub gist: GistArg,
+    /// Gist to operate on, if any.
+    pub gist: Option<GistArg>,
     /// Arguments to the gist, if any.
     /// This is only used if command == Command::Run.
     pub gist_args: Option<Vec<String>>,
@@ -159,9 +159,10 @@ impl<'a> TryFrom<ArgMatches<'a>> for Options {
         let command = Command::from_str(cmd).unwrap_or(Command::Run);
 
         // Parse out the gist argument.
-        let gist = try!(GistArg::from_str(
-            cmd_matches.value_of(ARG_GIST).unwrap()
-        ));
+        let gist = match cmd_matches.value_of(ARG_GIST) {
+            Some(g) => Some(try!(GistArg::from_str(g))),
+            None => None,
+        };
 
         // For the "run" command, arguments may be provided.
         let mut gist_args = cmd_matches.values_of(ARG_GIST_ARGV)
@@ -557,4 +558,12 @@ mod tests {
         assert!(parse_from_argv(args).is_err(),
             "\"help\" command was incorrectly treated as gist command");
     }
+
+    /// Verify that you can call the program with just the verbosity flags.
+    #[test]
+    fn just_verbosity_works() {
+        let args = vec!["gisht", "-v"];
+        assert!(parse_from_argv(args).is_ok(),
+            "Failed to parse command line with just the verbosity args");
+    }
 }

src/main.rs

@@ -138,7 +138,7 @@ fn main() {
 fn print_args_error(e: ArgsError) -> io::Result<()> {
     match e {
         ArgsError::Parse(ref e) =>
-            // In case of generic parse error,
+            // In case of a generic parse error,
             // message provided by the clap library will be the usage string.
             writeln!(&mut io::stderr(), "{}", e.message),
         e => {
@@ -206,12 +206,17 @@ fn ensure_app_dir(opts: &Options) -> Result<(), ExitCode> {
 /// This may include fetching a fresh gist from a host, or updating it.
 /// If an error occurred, returns the corresponding exit code.
 fn decode_gist(opts: &Options) -> Result<Gist, ExitCode> {
-    let gist = match opts.gist {
-        GistArg::Uri(ref uri) => {
+    if opts.gist.is_none() {
+        error!("No gist provided. Try --help?");
+        return Err(exitcode::USAGE);
+    }
+
+    let gist = match opts.gist.as_ref().unwrap() {
+        &GistArg::Uri(ref uri) => {
             debug!("Gist {} specified as the argument", uri);
             Gist::from_uri(uri.clone())
         },
-        GistArg::BrowserUrl(ref url) => {
+        &GistArg::BrowserUrl(ref url) => {
             debug!("Gist URL `{}` specified as the argument", url);
             let url = url.as_str();
             let maybe_gist = try!(gist_from_url(url));