improve formatting of 'show'

src/core.rs

@@ -188,12 +188,24 @@ impl Pacdef {
     fn show_group_content(&self, groups: &ArgMatches) -> Result<()> {
         let mut iter = groups.get_many::<String>("group").unwrap().peekable();
 
+        let show_more_than_one_group = iter.size_hint().0 > 1;
+
         while let Some(arg_group) = iter.next() {
             let group = self
                 .groups
                 .iter()
                 .find(|g| g.name == *arg_group)
                 .ok_or_else(|| anyhow!("group {} not found", *arg_group))?;
+
+            if show_more_than_one_group {
+                let name = &group.name;
+                println!("{name}");
+                for _ in 0..name.len() {
+                    print!("-");
+                }
+                println!();
+            }
+
             println!("{group}");
             if iter.peek().is_some() {
                 println!();

src/grouping/group.rs

@@ -136,7 +136,7 @@ impl Display for Group {
         while let Some(section) = iter.next() {
             section.fmt(f)?;
             if iter.peek().is_some() {
-                f.write_char('\n')?;
+                f.write_str("\n\n")?;
             }
         }
         Ok(())

src/search.rs

@@ -2,7 +2,7 @@ use std::collections::HashSet;
 use std::iter::Peekable;
 use std::vec::IntoIter;
 
-use anyhow::{Context, Result};
+use anyhow::{bail, Context, Result};
 use clap::ArgMatches;
 use regex::Regex;
 
@@ -27,6 +27,10 @@ pub(crate) fn search_packages(args: &ArgMatches, groups: &HashSet<Group>) -> Res
         }
     }
 
+    if vec.is_empty() {
+        bail!("no packages matching query")
+    }
+
     print_triples(vec);
 
     Ok(())