add 'task modify' (that can only modify description right now)

cli/src/cmd/mod.rs

@@ -9,6 +9,7 @@ mod add;
 mod gc;
 mod info;
 mod list;
+mod modify;
 mod pending;
 mod sync;
 
@@ -17,9 +18,10 @@ pub(crate) fn subcommands() -> Vec<Box<dyn SubCommand>> {
     vec![
         add::cmd(),
         gc::cmd(),
-        list::cmd(),
-        pending::cmd(),
         info::cmd(),
+        list::cmd(),
+        modify::cmd(),
+        pending::cmd(),
         sync::cmd(),
     ]
 }

cli/src/cmd/modify.rs

@@ -0,0 +1,63 @@
+use crate::cmd::shared;
+use clap::{App, Arg, ArgMatches, SubCommand as ClapSubCommand};
+use failure::Fallible;
+
+use crate::cmd::{ArgMatchResult, CommandInvocation};
+
+#[derive(Debug)]
+struct Invocation {
+    task: String,
+    description: String,
+}
+
+define_subcommand! {
+    fn decorate_app<'a>(&self, app: App<'a, 'a>) -> App<'a, 'a> {
+        app.subcommand(
+            ClapSubCommand::with_name("modify").about("modifies a task")
+                .arg(shared::task_arg())
+            .arg(
+                Arg::with_name("description")
+                    .help("task description")
+                    .required(true),
+            ),
+        )
+    }
+
+    fn arg_match<'a>(&self, matches: &ArgMatches<'a>) -> ArgMatchResult {
+        match matches.subcommand() {
+            ("modify", Some(matches)) => ArgMatchResult::Ok(Box::new(Invocation {
+                task: matches.value_of("task").unwrap().into(),
+                description: matches.value_of("description").unwrap().into(),
+            })),
+            _ => ArgMatchResult::None,
+        }
+    }
+}
+
+subcommand_invocation! {
+    fn run(&self, command: &CommandInvocation) -> Fallible<()> {
+        let mut replica = command.get_replica();
+        let task = shared::get_task(&mut replica, &self.task)?;
+
+        let mut task = task.into_mut(&mut replica);
+        task.set_description(self.description.clone())?;
+        println!("modified task {}", task.get_uuid());
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn parse_command() {
+        with_subcommand_invocation!(
+            vec!["task", "modify", "2", "foo bar"],
+            |inv: &Invocation| {
+                assert_eq!(inv.task, "2".to_string());
+                assert_eq!(inv.description, "foo bar".to_string());
+            }
+        );
+    }
+}