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, 770 insertions, 0 deletions

diff --git a/third_party/git/t/t6426-merge-skip-unneeded-updates.sh b/third_party/git/t/t6426-merge-skip-unneeded-updates.sh
new file mode 100755
index 000000000000..699813671c8c
--- /dev/null
+++ b/third_party/git/t/t6426-merge-skip-unneeded-updates.sh
@@ -0,0 +1,770 @@
+#!/bin/sh
+
+test_description="merge cases"
+
+# The setup for all of them, pictorially, is:
+#
+#      A
+#      o
+#     / \
+#  O o   ?
+#     \ /
+#      o
+#      B
+#
+# To help make it easier to follow the flow of tests, they have been
+# divided into sections and each test will start with a quick explanation
+# of what commits O, A, and B contain.
+#
+# Notation:
+#    z/{b,c}   means  files z/b and z/c both exist
+#    x/d_1     means  file x/d exists with content d1.  (Purpose of the
+#                     underscore notation is to differentiate different
+#                     files that might be renamed into each other's paths.)
+
+. ./test-lib.sh
+
+
+###########################################################################
+# SECTION 1: Cases involving no renames (one side has subset of changes of
+#            the other side)
+###########################################################################
+
+# Testcase 1a, Changes on A, subset of changes on B
+#   Commit O: b_1
+#   Commit A: b_2
+#   Commit B: b_3
+#   Expected: b_2
+
+test_setup_1a () {
+	test_create_repo 1a_$1 &&
+	(
+		cd 1a_$1 &&
+
+		test_write_lines 1 2 3 4 5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 10.5 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '1a-L: Modify(A)/Modify(B), change on B subset of A' '
+	test_setup_1a L &&
+	(
+		cd 1a_L &&
+
+		git checkout A^0 &&
+
+		test-tool chmtime --get -3600 b >old-mtime &&
+
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		# Make sure b was NOT updated
+		test-tool chmtime --get b >new-mtime &&
+		test_cmp old-mtime new-mtime &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:b &&
+		git rev-parse >expect A:b &&
+		test_cmp expect actual &&
+
+		git hash-object b   >actual &&
+		git rev-parse   A:b >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '1a-R: Modify(A)/Modify(B), change on B subset of A' '
+	test_setup_1a R &&
+	(
+		cd 1a_R &&
+
+		git checkout B^0 &&
+
+		test-tool chmtime --get -3600 b >old-mtime &&
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive A^0 >out 2>err &&
+
+		# Make sure b WAS updated
+		test-tool chmtime --get b >new-mtime &&
+		test $(cat old-mtime) -lt $(cat new-mtime) &&
+
+		test_must_be_empty err &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:b &&
+		git rev-parse >expect A:b &&
+		test_cmp expect actual &&
+
+		git hash-object b   >actual &&
+		git rev-parse   A:b >expect &&
+		test_cmp expect actual
+	)
+'
+
+
+###########################################################################
+# SECTION 2: Cases involving basic renames
+###########################################################################
+
+# Testcase 2a, Changes on A, rename on B
+#   Commit O: b_1
+#   Commit A: b_2
+#   Commit B: c_1
+#   Expected: c_2
+
+test_setup_2a () {
+	test_create_repo 2a_$1 &&
+	(
+		cd 2a_$1 &&
+
+		test_seq 1 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_seq 1 11 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		git mv b c &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '2a-L: Modify/rename, merge into modify side' '
+	test_setup_2a L &&
+	(
+		cd 2a_L &&
+
+		git checkout A^0 &&
+
+		test_path_is_missing c &&
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err &&
+
+		test_path_is_file c &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:c &&
+		git rev-parse >expect A:b &&
+		test_cmp expect actual &&
+
+		git hash-object c   >actual &&
+		git rev-parse   A:b >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:b &&
+		test_path_is_missing b
+	)
+'
+
+test_expect_success '2a-R: Modify/rename, merge into rename side' '
+	test_setup_2a R &&
+	(
+		cd 2a_R &&
+
+		git checkout B^0 &&
+
+		test-tool chmtime --get -3600 c >old-mtime &&
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive A^0 >out 2>err &&
+
+		# Make sure c WAS updated
+		test-tool chmtime --get c >new-mtime &&
+		test $(cat old-mtime) -lt $(cat new-mtime) &&
+
+		test_must_be_empty err &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:c &&
+		git rev-parse >expect A:b &&
+		test_cmp expect actual &&
+
+		git hash-object c   >actual &&
+		git rev-parse   A:b >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:b &&
+		test_path_is_missing b
+	)
+'
+
+# Testcase 2b, Changed and renamed on A, subset of changes on B
+#   Commit O: b_1
+#   Commit A: c_2
+#   Commit B: b_3
+#   Expected: c_2
+
+test_setup_2b () {
+	test_create_repo 2b_$1 &&
+	(
+		cd 2b_$1 &&
+
+		test_write_lines 1 2 3 4 5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 10.5 >b &&
+		git add b &&
+		git mv b c &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '2b-L: Rename+Mod(A)/Mod(B), B mods subset of A' '
+	test_setup_2b L &&
+	(
+		cd 2b_L &&
+
+		git checkout A^0 &&
+
+		test-tool chmtime --get -3600 c >old-mtime &&
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		# Make sure c WAS updated
+		test-tool chmtime --get c >new-mtime &&
+		test_cmp old-mtime new-mtime &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:c &&
+		git rev-parse >expect A:c &&
+		test_cmp expect actual &&
+
+		git hash-object c   >actual &&
+		git rev-parse   A:c >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:b &&
+		test_path_is_missing b
+	)
+'
+
+test_expect_success '2b-R: Rename+Mod(A)/Mod(B), B mods subset of A' '
+	test_setup_2b R &&
+	(
+		cd 2b_R &&
+
+		git checkout B^0 &&
+
+		test_path_is_missing c &&
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive A^0 >out 2>err &&
+
+		# Make sure c now present (and thus was updated)
+		test_path_is_file c &&
+
+		test_must_be_empty err &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual HEAD:c &&
+		git rev-parse >expect A:c &&
+		test_cmp expect actual &&
+
+		git hash-object c   >actual &&
+		git rev-parse   A:c >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:b &&
+		test_path_is_missing b
+	)
+'
+
+# Testcase 2c, Changes on A, rename on B
+#   Commit O: b_1
+#   Commit A: b_2, c_3
+#   Commit B: c_1
+#   Expected: rename/add conflict c_2 vs c_3
+#
+#   NOTE: Since A modified b_1->b_2, and B renamed b_1->c_1, the threeway
+#         merge of those files should result in c_2.  We then should have a
+#         rename/add conflict between c_2 and c_3.  However, if we note in
+#         merge_content() that A had the right contents (b_2 has same
+#         contents as c_2, just at a different name), and that A had the
+#         right path present (c_3 existed) and thus decides that it can
+#         skip the update, then we're in trouble.  This test verifies we do
+#         not make that particular mistake.
+
+test_setup_2c () {
+	test_create_repo 2c &&
+	(
+		cd 2c &&
+
+		test_seq 1 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_seq 1 11 >b &&
+		echo whatever >c &&
+		git add b c &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		git mv b c &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '2c: Modify b & add c VS rename b->c' '
+	test_setup_2c &&
+	(
+		cd 2c &&
+
+		git checkout A^0 &&
+
+		test-tool chmtime --get -3600 c >old-mtime &&
+		GIT_MERGE_VERBOSITY=3 &&
+		export GIT_MERGE_VERBOSITY &&
+		test_must_fail git merge -s recursive B^0 >out 2>err &&
+
+		test_i18ngrep "CONFLICT (.*/add):" out &&
+		test_must_be_empty err &&
+
+		# Make sure c WAS updated
+		test-tool chmtime --get c >new-mtime &&
+		test $(cat old-mtime) -lt $(cat new-mtime)
+
+		# FIXME: rename/add conflicts are horribly broken right now;
+		# when I get back to my patch series fixing it and
+		# rename/rename(2to1) conflicts to bring them in line with
+		# how add/add conflicts behave, then checks like the below
+		# could be added.  But that patch series is waiting until
+		# the rename-directory-detection series lands, which this
+		# is part of.  And in the mean time, I do not want to further
+		# enforce broken behavior.  So for now, the main test is the
+		# one above that err is an empty file.
+
+		#git ls-files -s >index_files &&
+		#test_line_count = 2 index_files &&
+
+		#git rev-parse >actual :2:c :3:c &&
+		#git rev-parse >expect A:b  A:c  &&
+		#test_cmp expect actual &&
+
+		#git cat-file -p A:b >>merged &&
+		#git cat-file -p A:c >>merge-me &&
+		#>empty &&
+		#test_must_fail git merge-file \
+		#	-L "Temporary merge branch 1" \
+		#	-L "" \
+		#	-L "Temporary merge branch 2" \
+		#	merged empty merge-me &&
+		#sed -e "s/^\([<=>]\)/\1\1\1/" merged >merged-internal &&
+
+		#git hash-object c               >actual &&
+		#git hash-object merged-internal >expect &&
+		#test_cmp expect actual &&
+
+		#test_path_is_missing b
+	)
+'
+
+
+###########################################################################
+# SECTION 3: Cases involving directory renames
+#
+# NOTE:
+#   Directory renames only apply when one side renames a directory, and the
+#   other side adds or renames a path into that directory.  Applying the
+#   directory rename to that new path creates a new pathname that didn't
+#   exist on either side of history.  Thus, it is impossible for the
+#   merge contents to already be at the right path, so all of these checks
+#   exist just to make sure that updates are not skipped.
+###########################################################################
+
+# Testcase 3a, Change + rename into dir foo on A, dir rename foo->bar on B
+#   Commit O: bq_1, foo/whatever
+#   Commit A: foo/{bq_2, whatever}
+#   Commit B: bq_1, bar/whatever
+#   Expected: bar/{bq_2, whatever}
+
+test_setup_3a () {
+	test_create_repo 3a_$1 &&
+	(
+		cd 3a_$1 &&
+
+		mkdir foo &&
+		test_seq 1 10 >bq &&
+		test_write_lines a b c d e f g h i j k >foo/whatever &&
+		git add bq foo/whatever &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_seq 1 11 >bq &&
+		git add bq &&
+		git mv bq foo/ &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		git mv foo/ bar/ &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '3a-L: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
+	test_setup_3a L &&
+	(
+		cd 3a_L &&
+
+		git checkout A^0 &&
+
+		test_path_is_missing bar/bq &&
+		GIT_MERGE_VERBOSITY=3 git -c merge.directoryRenames=true merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		test_path_is_file bar/bq &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 2 index_files &&
+
+		git rev-parse >actual HEAD:bar/bq HEAD:bar/whatever &&
+		git rev-parse >expect A:foo/bq    A:foo/whatever &&
+		test_cmp expect actual &&
+
+		git hash-object bar/bq   bar/whatever   >actual &&
+		git rev-parse   A:foo/bq A:foo/whatever >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
+		test_path_is_missing bq foo/bq foo/whatever
+	)
+'
+
+test_expect_success '3a-R: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
+	test_setup_3a R &&
+	(
+		cd 3a_R &&
+
+		git checkout B^0 &&
+
+		test_path_is_missing bar/bq &&
+		GIT_MERGE_VERBOSITY=3 git -c merge.directoryRenames=true merge -s recursive A^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		test_path_is_file bar/bq &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 2 index_files &&
+
+		git rev-parse >actual HEAD:bar/bq HEAD:bar/whatever &&
+		git rev-parse >expect A:foo/bq    A:foo/whatever &&
+		test_cmp expect actual &&
+
+		git hash-object bar/bq   bar/whatever   >actual &&
+		git rev-parse   A:foo/bq A:foo/whatever >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
+		test_path_is_missing bq foo/bq foo/whatever
+	)
+'
+
+# Testcase 3b, rename into dir foo on A, dir rename foo->bar + change on B
+#   Commit O: bq_1, foo/whatever
+#   Commit A: foo/{bq_1, whatever}
+#   Commit B: bq_2, bar/whatever
+#   Expected: bar/{bq_2, whatever}
+
+test_setup_3b () {
+	test_create_repo 3b_$1 &&
+	(
+		cd 3b_$1 &&
+
+		mkdir foo &&
+		test_seq 1 10 >bq &&
+		test_write_lines a b c d e f g h i j k >foo/whatever &&
+		git add bq foo/whatever &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		git mv bq foo/ &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		test_seq 1 11 >bq &&
+		git add bq &&
+		git mv foo/ bar/ &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '3b-L: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
+	test_setup_3b L &&
+	(
+		cd 3b_L &&
+
+		git checkout A^0 &&
+
+		test_path_is_missing bar/bq &&
+		GIT_MERGE_VERBOSITY=3 git -c merge.directoryRenames=true merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		test_path_is_file bar/bq &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 2 index_files &&
+
+		git rev-parse >actual HEAD:bar/bq HEAD:bar/whatever &&
+		git rev-parse >expect B:bq        A:foo/whatever &&
+		test_cmp expect actual &&
+
+		git hash-object bar/bq bar/whatever   >actual &&
+		git rev-parse   B:bq   A:foo/whatever >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
+		test_path_is_missing bq foo/bq foo/whatever
+	)
+'
+
+test_expect_success '3b-R: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
+	test_setup_3b R &&
+	(
+		cd 3b_R &&
+
+		git checkout B^0 &&
+
+		test_path_is_missing bar/bq &&
+		GIT_MERGE_VERBOSITY=3 git -c merge.directoryRenames=true merge -s recursive A^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		test_path_is_file bar/bq &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 2 index_files &&
+
+		git rev-parse >actual HEAD:bar/bq HEAD:bar/whatever &&
+		git rev-parse >expect B:bq        A:foo/whatever &&
+		test_cmp expect actual &&
+
+		git hash-object bar/bq bar/whatever   >actual &&
+		git rev-parse   B:bq   A:foo/whatever >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
+		test_path_is_missing bq foo/bq foo/whatever
+	)
+'
+
+###########################################################################
+# SECTION 4: Cases involving dirty changes
+###########################################################################
+
+# Testcase 4a, Changed on A, subset of changes on B, locally modified
+#   Commit O: b_1
+#   Commit A: b_2
+#   Commit B: b_3
+#   Working copy: b_4
+#   Expected: b_2 for merge, b_4 in working copy
+
+test_setup_4a () {
+	test_create_repo 4a &&
+	(
+		cd 4a &&
+
+		test_write_lines 1 2 3 4 5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 10.5 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+# NOTE: For as long as we continue using unpack_trees() without index_only
+#   set to true, it will error out on a case like this claiming that the locally
+#   modified file would be overwritten by the merge.  Getting this testcase
+#   correct requires doing the merge in-memory first, then realizing that no
+#   updates to the file are necessary, and thus that we can just leave the path
+#   alone.
+test_expect_failure '4a: Change on A, change on B subset of A, dirty mods present' '
+	test_setup_4a &&
+	(
+		cd 4a &&
+
+		git checkout A^0 &&
+		echo "File rewritten" >b &&
+
+		test-tool chmtime --get -3600 b >old-mtime &&
+
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		# Make sure b was NOT updated
+		test-tool chmtime --get b >new-mtime &&
+		test_cmp old-mtime new-mtime &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual :0:b &&
+		git rev-parse >expect A:b &&
+		test_cmp expect actual &&
+
+		git hash-object b >actual &&
+		echo "File rewritten" | git hash-object --stdin >expect &&
+		test_cmp expect actual
+	)
+'
+
+# Testcase 4b, Changed+renamed on A, subset of changes on B, locally modified
+#   Commit O: b_1
+#   Commit A: c_2
+#   Commit B: b_3
+#   Working copy: c_4
+#   Expected: c_2
+
+test_setup_4b () {
+	test_create_repo 4b &&
+	(
+		cd 4b &&
+
+		test_write_lines 1 2 3 4 5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 10.5 >b &&
+		git add b &&
+		git mv b c &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		test_write_lines 1 2 3 4 5 5.5 6 7 8 9 10 >b &&
+		git add b &&
+		test_tick &&
+		git commit -m "B"
+	)
+}
+
+test_expect_success '4b: Rename+Mod(A)/Mod(B), change on B subset of A, dirty mods present' '
+	test_setup_4b &&
+	(
+		cd 4b &&
+
+		git checkout A^0 &&
+		echo "File rewritten" >c &&
+
+		test-tool chmtime --get -3600 c >old-mtime &&
+
+		GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err &&
+
+		test_must_be_empty err &&
+
+		# Make sure c was NOT updated
+		test-tool chmtime --get c >new-mtime &&
+		test_cmp old-mtime new-mtime &&
+
+		git ls-files -s >index_files &&
+		test_line_count = 1 index_files &&
+
+		git rev-parse >actual :0:c &&
+		git rev-parse >expect A:c &&
+		test_cmp expect actual &&
+
+		git hash-object c >actual &&
+		echo "File rewritten" | git hash-object --stdin >expect &&
+		test_cmp expect actual &&
+
+		test_must_fail git rev-parse HEAD:b &&
+		test_path_is_missing b
+	)
+'
+
+test_done