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, 216 insertions, 0 deletions

diff --git a/third_party/git/t/t6424-merge-unrelated-index-changes.sh b/third_party/git/t/t6424-merge-unrelated-index-changes.sh
new file mode 100755
index 000000000000..5e3779ebc931
--- /dev/null
+++ b/third_party/git/t/t6424-merge-unrelated-index-changes.sh
@@ -0,0 +1,216 @@
+#!/bin/sh
+
+test_description="merges with unrelated index changes"
+
+. ./test-lib.sh
+
+# Testcase for some simple merges
+#   A
+#   o-------o B
+#    \
+#     \-----o C
+#      \
+#       \---o D
+#        \
+#         \-o E
+#          \
+#           o F
+#   Commit A: some file a
+#   Commit B: adds file b, modifies end of a
+#   Commit C: adds file c
+#   Commit D: adds file d, modifies beginning of a
+#   Commit E: renames a->subdir/a, adds subdir/e
+#   Commit F: empty commit
+
+test_expect_success 'setup trivial merges' '
+	test_seq 1 10 >a &&
+	git add a &&
+	test_tick && git commit -m A &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+	git branch D &&
+	git branch E &&
+	git branch F &&
+
+	git checkout B &&
+	echo b >b &&
+	echo 11 >>a &&
+	git add a b &&
+	test_tick && git commit -m B &&
+
+	git checkout C &&
+	echo c >c &&
+	git add c &&
+	test_tick && git commit -m C &&
+
+	git checkout D &&
+	test_seq 2 10 >a &&
+	echo d >d &&
+	git add a d &&
+	test_tick && git commit -m D &&
+
+	git checkout E &&
+	mkdir subdir &&
+	git mv a subdir/a &&
+	echo e >subdir/e &&
+	git add subdir &&
+	test_tick && git commit -m E &&
+
+	git checkout F &&
+	test_tick && git commit --allow-empty -m F
+'
+
+test_expect_success 'ff update' '
+	git reset --hard &&
+	git checkout A^0 &&
+
+	touch random_file && git add random_file &&
+
+	git merge E^0 &&
+
+	test_must_fail git rev-parse HEAD:random_file &&
+	test "$(git diff --name-only --cached E)" = "random_file"
+'
+
+test_expect_success 'ff update, important file modified' '
+	git reset --hard &&
+	git checkout A^0 &&
+
+	mkdir subdir &&
+	touch subdir/e &&
+	git add subdir/e &&
+
+	test_must_fail git merge E^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'resolve, trivial' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s resolve C^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'resolve, non-trivial' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s resolve D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'recursive' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s recursive C^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'recursive, when merge branch matches merge base' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s recursive F^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'merge-recursive, when index==head but head!=HEAD' '
+	git reset --hard &&
+	git checkout C^0 &&
+
+	# Make index match B
+	git diff C B -- | git apply --cached &&
+	# Merge B & F, with B as "head"
+	git merge-recursive A -- B F > out &&
+	test_i18ngrep "Already up to date" out
+'
+
+test_expect_success 'recursive, when file has staged changes not matching HEAD nor what a merge would give' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	mkdir subdir &&
+	test_seq 1 10 >subdir/a &&
+	git add subdir/a &&
+
+	# We have staged changes; merge should error out
+	test_must_fail git merge -s recursive E^0 2>err &&
+	test_i18ngrep "changes to the following files would be overwritten" err
+'
+
+test_expect_success 'recursive, when file has staged changes matching what a merge would give' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	mkdir subdir &&
+	test_seq 1 11 >subdir/a &&
+	git add subdir/a &&
+
+	# We have staged changes; merge should error out
+	test_must_fail git merge -s recursive E^0 2>err &&
+	test_i18ngrep "changes to the following files would be overwritten" err
+'
+
+test_expect_success 'octopus, unrelated file touched' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'octopus, related file removed' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	git rm b &&
+
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'octopus, related file modified' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	echo 12 >>a && git add a &&
+
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'ours' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s ours C^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'subtree' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	touch random_file && git add random_file &&
+
+	test_must_fail git merge -s subtree E^0 &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_done