scalar: disable orphaned commit checks by default

Checking for commits left behind when leaving a detached HEAD can
be expensive in large repositories. Add
checkout.orphanedCommitWarning=false to Scalar's recommended settings
to avoid this foreground work while preserving normal checkout output.

Use the existing set-if-missing behavior so clone, register, and
reconfigure preserve explicit user choices. Document the tradeoff
and test the default and override handling.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b6f500b7-ce3c-4a1f-bc56-594b8f971a80

Author: Wyatt Holden

Documentation/scalar.adoc

@@ -214,6 +214,13 @@ am.keepCR=true::
 	and non-Windows platforms and keeping carriage return (`\r`) characters
 	in certain workflows.
 
+checkout.orphanedCommitWarning=false::
+	This disables the reachability check that warns about commits left
+	behind when `git checkout` or `git switch` leaves a detached `HEAD`.
+	The check can be expensive in large repositories. Other checkout
+	output is unchanged, and commits left behind can still be found
+	in the `HEAD` reflog until its entries expire.
+
 commitGraph.changedPaths=true::
 	This setting helps the background maintenance steps that compute the
 	serialized commit-graph to also store changed-path Bloom filters. This

scalar.c

@@ -138,6 +138,7 @@ static int set_recommended_config(int reconfigure)
 	 */
 	struct scalar_config config[] = {
 		{ "am.keepCR", "true" },
+		{ "checkout.orphanedCommitWarning", "false" },
 		{ "commitGraph.changedPaths", "true" },
 		{ "commitGraph.generationVersion", "1" },
 		{ "core.autoCRLF", "false" },

t/t9210-scalar.sh

@@ -140,6 +140,23 @@ test_expect_success 'scalar register --no-maintenance' '
 	test_subcommand ! git maintenance unregister --force <no-maint.event
 '
 
+test_expect_success 'scalar disables orphan checks without overriding user configuration' '
+	test_when_finished "scalar unregister orphan-check" &&
+	git init orphan-check &&
+	scalar register --no-maintenance orphan-check &&
+	test_cmp_config -C orphan-check false checkout.orphanedCommitWarning &&
+
+	git -C orphan-check config unset checkout.orphanedCommitWarning &&
+	scalar reconfigure --maintenance=keep orphan-check &&
+	test_cmp_config -C orphan-check false checkout.orphanedCommitWarning &&
+
+	git -C orphan-check config set checkout.orphanedCommitWarning true &&
+	scalar register --no-maintenance orphan-check &&
+	test_cmp_config -C orphan-check true checkout.orphanedCommitWarning &&
+	scalar reconfigure --maintenance=keep orphan-check &&
+	test_cmp_config -C orphan-check true checkout.orphanedCommitWarning
+'
+
 test_expect_success 'set up repository to clone' '
 	test_commit first &&
 	test_commit second &&
@@ -161,6 +178,8 @@ test_expect_success 'scalar clone' '
 	(
 		cd cloned/src &&
 
+		test_cmp_config false checkout.orphanedCommitWarning &&
+
 		git config --get --global --fixed-value maintenance.repo \
 			"$(pwd)" &&