fix(lock): In error, differentiate between creating and updating lockfile (#16227)

### What does this PR try to resolve?

Fixes #10503

### How to test and review this PR?

Author: weihanglo

src/cargo/ops/lockfile.rs

@@ -53,13 +53,17 @@ pub fn write_pkg_lockfile(ws: &Workspace<'_>, resolve: &mut Resolve) -> CargoRes
     }
 
     if let Some(locked_flag) = ws.gctx().locked_flag() {
+        let lockfile_path = lock_root.as_path_unlocked().join(LOCKFILE_NAME);
+        let action = if lockfile_path.exists() {
+            "updated"
+        } else {
+            "created"
+        };
+        let lockfile_path = lockfile_path.display();
         anyhow::bail!(
-            "the lock file {} needs to be updated but {} was passed to prevent this\n\
-             If you want to try to generate the lock file without accessing the network, \
-             remove the {} flag and use --offline instead.",
-            lock_root.as_path_unlocked().join(LOCKFILE_NAME).display(),
-            locked_flag,
-            locked_flag
+            "the lock file {lockfile_path} needs to be {action} but {locked_flag} was passed to prevent this\n\
+             help: to generate the lock file without accessing the network, \
+             remove the {locked_flag} flag and use --offline instead."
         );
     }
 

tests/testsuite/lockfile_compat.rs

@@ -517,8 +517,8 @@ fn locked_correct_error() {
         .with_status(101)
         .with_stderr_data(str![[r#"
 [UPDATING] `dummy-registry` index
-[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be updated but --locked was passed to prevent this
-If you want to try to generate the lock file without accessing the network, remove the --locked flag and use --offline instead.
+[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be created but --locked was passed to prevent this
+[HELP] to generate the lock file without accessing the network, remove the --locked flag and use --offline instead.
 
 "#]])
         .run();

tests/testsuite/offline.rs

@@ -767,8 +767,8 @@ fn offline_and_frozen_and_no_lock() {
     p.cargo("check --frozen --offline")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be updated but --frozen was passed to prevent this
-If you want to try to generate the lock file without accessing the network, remove the --frozen flag and use --offline instead.
+[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be created but --frozen was passed to prevent this
+[HELP] to generate the lock file without accessing the network, remove the --frozen flag and use --offline instead.
 
 "#]])
         .run();
@@ -780,8 +780,8 @@ fn offline_and_locked_and_no_frozen() {
     p.cargo("check --locked --offline")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be updated but --locked was passed to prevent this
-If you want to try to generate the lock file without accessing the network, remove the --locked flag and use --offline instead.
+[ERROR] the lock file [ROOT]/foo/Cargo.lock needs to be created but --locked was passed to prevent this
+[HELP] to generate the lock file without accessing the network, remove the --locked flag and use --offline instead.
 
 "#]])
         .run();