doc: Minor UI fixes for the new lock strategy arguments (#2329)

* fix: improve lock strategy group name and argument help text.

* fix: improve PdmUsageError message when supplying invalid strategy flag.

Before/after:

    $ pdm run pdm lock -S someflag
    [PdmUsageError]: Invalid strategy flag: someflag, supported: frozenset({'static_urls', 'cross_platform', 'direct_minimal_versions'})
    $ pdm run pdm lock -S someflag
    [PdmUsageError]: Invalid strategy flag: someflag, supported: static_urls, direct_minimal_versions, cross_platform

src/pdm/cli/options.py

@@ -187,7 +187,7 @@ def no_isolation_option(project: Project, namespace: argparse.Namespace, values:
 
 install_group.options.append(no_isolation_option)
 
-groups_group = ArgumentGroup("Dependencies selection")
+groups_group = ArgumentGroup("Dependencies Selection")
 groups_group.add_argument(
     "-G",
     "--group",
@@ -365,15 +365,15 @@ def ignore_python_option(project: Project, namespace: argparse.Namespace, values
 )
 
 
-lock_strategy_group = ArgumentGroup("lock_strategy")
+lock_strategy_group = ArgumentGroup("Lock Strategy")
 lock_strategy_group.add_argument(
     "--strategy",
     "-S",
     dest="strategy_change",
     metavar="STRATEGY",
     action=split_lists(","),
-    help="Specify lock strategy(cross_platform,static_urls,direct_minimal_versions). Add 'no_' prefix to disable."
-    " Support given multiple times or split by comma.",
+    help="Specify lock strategy (cross_platform, static_urls, direct_minimal_versions). Add 'no_' prefix to disable."
+    " Can be supplied multiple times or split by comma.",
 )
 lock_strategy_group.add_argument(
     "--no-cross-platform",

src/pdm/project/lockfile.py

@@ -50,11 +50,11 @@ def apply_strategy_change(self, changes: Iterable[str]) -> set[str]:
             change = change.replace("-", "_").lower()
             if change.startswith("no_"):
                 if change[3:] not in SUPPORTED_FLAGS:
-                    raise PdmUsageError(f"Invalid strategy flag: {change[3:]}, supported: {SUPPORTED_FLAGS}")
+                    raise PdmUsageError(f"Invalid strategy flag: {change[3:]}, supported: {', '.join(SUPPORTED_FLAGS)}")
                 original.discard(change[3:])
             else:
                 if change not in SUPPORTED_FLAGS:
-                    raise PdmUsageError(f"Invalid strategy flag: {change}, supported: {SUPPORTED_FLAGS}")
+                    raise PdmUsageError(f"Invalid strategy flag: {change}, supported: {', '.join(SUPPORTED_FLAGS)}")
                 original.add(change)
         return original