meli: add print-used-paths subcommand

Print all paths that meli creates/uses e.g. XDG data path and temp dir
path.

Signed-off-by: Manos Pitsidianakis <manos@pitsidianak.is>

meli/docs/meli.1

@@ -79,6 +79,8 @@ Print documentation page and exit (Piping to a pager is recommended).
 Print default theme keys and values in TOML syntax, to be used as a blueprint.
 .It Cm print-loaded-themes
 Print all loaded themes in TOML syntax.
+.It Cm print-used-paths
+Print all paths that meli creates/uses.
 .It Cm compiled-with
 Print compile time feature flags of this binary.
 .It Cm view

meli/src/args.rs

@@ -65,6 +65,8 @@ pub enum SubCommand {
     PrintDefaultTheme,
     /// print loaded themes in full to stdout and exit.
     PrintLoadedThemes,
+    /// print all paths that meli creates/uses.
+    PrintUsedPaths,
     /// edit configuration files with `$EDITOR`/`$VISUAL`.
     EditConfig,
     /// create a sample configuration file with available configuration options.

meli/src/main.rs

@@ -117,6 +117,22 @@ fn run_app(opt: Opt) -> Result<()> {
             return Ok(());
         }
         Some(SubCommand::View { .. }) => {}
+        Some(SubCommand::PrintUsedPaths) => {
+            println!(
+                "{}",
+                xdg::BaseDirectories::with_prefix("meli")
+                    .expect(
+                        "Could not find your XDG directories. If this is unexpected, please \
+                         report it as a bug."
+                    )
+                    .get_data_file("")
+                    .display()
+            );
+            let mut temp_dir = std::env::temp_dir();
+            temp_dir.push("meli");
+            println!("{}", temp_dir.display());
+            return Ok(());
+        }
         None => {}
     }