merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/t/t6039-merge-ignorecase.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+
+test_description='git-merge with case-changing rename on case-insensitive file system'
+
+. ./test-lib.sh
+
+if ! test_have_prereq CASE_INSENSITIVE_FS
+then
+	skip_all='skipping case insensitive tests - case sensitive file system'
+	test_done
+fi
+
+test_expect_success 'merge with case-changing rename' '
+	test $(git config core.ignorecase) = true &&
+	>TestCase &&
+	git add TestCase &&
+	git commit -m "add TestCase" &&
+	git tag baseline &&
+	git checkout -b with-camel &&
+	>foo &&
+	git add foo &&
+	git commit -m "intervening commit" &&
+	git checkout master &&
+	git rm TestCase &&
+	>testcase &&
+	git add testcase &&
+	git commit -m "rename to testcase" &&
+	git checkout with-camel &&
+	git merge master -m "merge" &&
+	test_path_is_file testcase
+'
+
+test_expect_success 'merge with case-changing rename on both sides' '
+	git checkout master &&
+	git reset --hard baseline &&
+	git branch -D with-camel &&
+	git checkout -b with-camel &&
+	git mv TestCase testcase &&
+	git commit -m "recase on branch" &&
+	>foo &&
+	git add foo &&
+	git commit -m "intervening commit" &&
+	git checkout master &&
+	git rm TestCase &&
+	>testcase &&
+	git add testcase &&
+	git commit -m "rename to testcase" &&
+	git checkout with-camel &&
+	git merge master -m "merge" &&
+	test_path_is_file testcase
+'
+
+test_done