Add context message before listing available tools when no arguments …

…are provided

Adds a helpful context message when `uvx` is run without arguments
to clarify that it is displaying the installed tools.

This addresses confusion, such as the one highlighted in issue astral-sh#7348,
by making the output more user-friendly and informative.

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

crates/uv/src/commands/tool/list.rs

@@ -69,6 +69,7 @@ pub(crate) async fn list(
             String::new()
         };
 
+        writeln!(printer.stdout(), "Installed tools:\n")?;
         if show_paths {
             writeln!(
                 printer.stdout(),

crates/uv/tests/tool_list.rs

@@ -30,6 +30,8 @@ fn tool_list() {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0
     - black
     - blackd
@@ -59,6 +61,8 @@ fn tool_list_paths() {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0 ([TEMP_DIR]/tools/black)
     - black ([TEMP_DIR]/bin/black)
     - blackd ([TEMP_DIR]/bin/blackd)
@@ -155,6 +159,8 @@ fn tool_list_bad_environment() -> Result<()> {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     ruff v0.3.4
     - ruff
 
@@ -218,6 +224,8 @@ fn tool_list_deprecated() -> Result<()> {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0
     - black
     - blackd
@@ -274,6 +282,8 @@ fn tool_list_show_version_specifiers() {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0 [required: <24.3.0]
     - black
     - blackd
@@ -288,6 +298,8 @@ fn tool_list_show_version_specifiers() {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0 [required: <24.3.0] ([TEMP_DIR]/tools/black)
     - black ([TEMP_DIR]/bin/black)
     - blackd ([TEMP_DIR]/bin/blackd)

crates/uv/tests/tool_run.rs

@@ -774,6 +774,8 @@ fn tool_run_list_installed() {
     success: true
     exit_code: 0
     ----- stdout -----
+    Installed tools:
+
     black v24.2.0
     - black
     - blackd