merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 172 insertions, 0 deletions

diff --git a/third_party/git/t/t6415-merge-dir-to-symlink.sh b/third_party/git/t/t6415-merge-dir-to-symlink.sh
new file mode 100755
index 000000000000..2eddcc7664e8
--- /dev/null
+++ b/third_party/git/t/t6415-merge-dir-to-symlink.sh
@@ -0,0 +1,172 @@
+#!/bin/sh
+
+test_description='merging when a directory was replaced with a symlink'
+. ./test-lib.sh
+
+test_expect_success 'create a commit where dir a/b changed to symlink' '
+	mkdir -p a/b/c a/b-2/c &&
+	> a/b/c/d &&
+	> a/b-2/c/d &&
+	> a/x &&
+	git add -A &&
+	git commit -m base &&
+	git tag start &&
+	rm -rf a/b &&
+	git add -A &&
+	test_ln_s_add b-2 a/b &&
+	git commit -m "dir to symlink"
+'
+
+test_expect_success 'checkout does not clobber untracked symlink' '
+	git checkout HEAD^0 &&
+	git reset --hard master &&
+	git rm --cached a/b &&
+	git commit -m "untracked symlink remains" &&
+	test_must_fail git checkout start^0
+'
+
+test_expect_success 'a/b-2/c/d is kept when clobbering symlink b' '
+	git checkout HEAD^0 &&
+	git reset --hard master &&
+	git rm --cached a/b &&
+	git commit -m "untracked symlink remains" &&
+	git checkout -f start^0 &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success 'checkout should not have deleted a/b-2/c/d' '
+	git checkout HEAD^0 &&
+	git reset --hard master &&
+	 git checkout start^0 &&
+	 test_path_is_file a/b-2/c/d
+'
+
+test_expect_success 'setup for merge test' '
+	git reset --hard &&
+	test_path_is_file a/b-2/c/d &&
+	echo x > a/x &&
+	git add a/x &&
+	git commit -m x &&
+	git tag baseline
+'
+
+test_expect_success 'Handle D/F conflict, do not lose a/b-2/c/d in merge (resolve)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	git merge -s resolve master &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success SYMLINKS 'a/b was resolved as symlink' '
+	test -h a/b
+'
+
+test_expect_success 'Handle D/F conflict, do not lose a/b-2/c/d in merge (recursive)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	git merge -s recursive master &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success SYMLINKS 'a/b was resolved as symlink' '
+	test -h a/b
+'
+
+test_expect_success 'Handle F/D conflict, do not lose a/b-2/c/d in merge (resolve)' '
+	git reset --hard &&
+	git checkout master^0 &&
+	git merge -s resolve baseline^0 &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success SYMLINKS 'a/b was resolved as symlink' '
+	test -h a/b
+'
+
+test_expect_success 'Handle F/D conflict, do not lose a/b-2/c/d in merge (recursive)' '
+	git reset --hard &&
+	git checkout master^0 &&
+	git merge -s recursive baseline^0 &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success SYMLINKS 'a/b was resolved as symlink' '
+	test -h a/b
+'
+
+test_expect_failure 'do not lose untracked in merge (resolve)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	>a/b/c/e &&
+	test_must_fail git merge -s resolve master &&
+	test_path_is_file a/b/c/e &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success 'do not lose untracked in merge (recursive)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	>a/b/c/e &&
+	test_must_fail git merge -s recursive master &&
+	test_path_is_file a/b/c/e &&
+	test_path_is_file a/b-2/c/d
+'
+
+test_expect_success 'do not lose modifications in merge (resolve)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	echo more content >>a/b/c/d &&
+	test_must_fail git merge -s resolve master
+'
+
+test_expect_success 'do not lose modifications in merge (recursive)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	echo more content >>a/b/c/d &&
+	test_must_fail git merge -s recursive master
+'
+
+test_expect_success 'setup a merge where dir a/b-2 changed to symlink' '
+	git reset --hard &&
+	git checkout start^0 &&
+	rm -rf a/b-2 &&
+	git add -A &&
+	test_ln_s_add b a/b-2 &&
+	git commit -m "dir a/b-2 to symlink" &&
+	git tag test2
+'
+
+test_expect_success 'merge should not have D/F conflicts (resolve)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	git merge -s resolve test2 &&
+	test_path_is_file a/b/c/d
+'
+
+test_expect_success SYMLINKS 'a/b-2 was resolved as symlink' '
+	test -h a/b-2
+'
+
+test_expect_success 'merge should not have D/F conflicts (recursive)' '
+	git reset --hard &&
+	git checkout baseline^0 &&
+	git merge -s recursive test2 &&
+	test_path_is_file a/b/c/d
+'
+
+test_expect_success SYMLINKS 'a/b-2 was resolved as symlink' '
+	test -h a/b-2
+'
+
+test_expect_success 'merge should not have F/D conflicts (recursive)' '
+	git reset --hard &&
+	git checkout -b foo test2 &&
+	git merge -s recursive baseline^0 &&
+	test_path_is_file a/b/c/d
+'
+
+test_expect_success SYMLINKS 'a/b-2 was resolved as symlink' '
+	test -h a/b-2
+'
+
+test_done