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

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

third_party/git/t/lib-read-tree-m-3way.sh

@@ -0,0 +1,158 @@
+: Included from t1000-read-tree-m-3way.sh and others
+# Original tree.
+mkdir Z
+for a in N D M
+do
+    for b in N D M
+    do
+        p=$a$b
+	echo This is $p from the original tree. >$p
+	echo This is Z/$p from the original tree. >Z/$p
+	test_expect_success \
+	    "adding test file $p and Z/$p" \
+	    'git update-index --add $p &&
+	    git update-index --add Z/$p'
+    done
+done
+echo This is SS from the original tree. >SS
+test_expect_success \
+    'adding test file SS' \
+    'git update-index --add SS'
+cat >TT <<\EOF
+This is a trivial merge sample text.
+Branch A is expected to upcase this word, here.
+There are some filler lines to avoid diff context
+conflicts here,
+like this one,
+and this one,
+and this one is yet another one of them.
+At the very end, here comes another line, that is
+the word, expected to be upcased by Branch B.
+This concludes the trivial merge sample file.
+EOF
+test_expect_success \
+    'adding test file TT' \
+    'git update-index --add TT'
+test_expect_success \
+    'prepare initial tree' \
+    'tree_O=$(git write-tree)'
+
+################################################################
+# Branch A and B makes the changes according to the above matrix.
+
+################################################################
+# Branch A
+
+to_remove=$(echo D? Z/D?)
+rm -f $to_remove
+test_expect_success \
+    'change in branch A (removal)' \
+    'git update-index --remove $to_remove'
+
+for p in M? Z/M?
+do
+    echo This is modified $p in the branch A. >$p
+    test_expect_success \
+	'change in branch A (modification)' \
+        "git update-index $p"
+done
+
+for p in AN AA Z/AN Z/AA
+do
+    echo This is added $p in the branch A. >$p
+    test_expect_success \
+	'change in branch A (addition)' \
+	"git update-index --add $p"
+done
+
+echo This is SS from the modified tree. >SS
+echo This is LL from the modified tree. >LL
+test_expect_success \
+    'change in branch A (addition)' \
+    'git update-index --add LL &&
+     git update-index SS'
+mv TT TT-
+sed -e '/Branch A/s/word/WORD/g' <TT- >TT
+rm -f TT-
+test_expect_success \
+    'change in branch A (edit)' \
+    'git update-index TT'
+
+mkdir DF
+echo Branch A makes a file at DF/DF, creating a directory DF. >DF/DF
+test_expect_success \
+    'change in branch A (change file to directory)' \
+    'git update-index --add DF/DF'
+
+test_expect_success \
+    'recording branch A tree' \
+    'tree_A=$(git write-tree)'
+
+################################################################
+# Branch B
+# Start from O
+
+rm -rf [NDMASLT][NDMASLT] Z DF
+mkdir Z
+test_expect_success \
+    'reading original tree and checking out' \
+    'git read-tree $tree_O &&
+     git checkout-index -a'
+
+to_remove=$(echo ?D Z/?D)
+rm -f $to_remove
+test_expect_success \
+    'change in branch B (removal)' \
+    "git update-index --remove $to_remove"
+
+for p in ?M Z/?M
+do
+    echo This is modified $p in the branch B. >$p
+    test_expect_success \
+	'change in branch B (modification)' \
+	"git update-index $p"
+done
+
+for p in NA AA Z/NA Z/AA
+do
+    echo This is added $p in the branch B. >$p
+    test_expect_success \
+	'change in branch B (addition)' \
+	"git update-index --add $p"
+done
+echo This is SS from the modified tree. >SS
+echo This is LL from the modified tree. >LL
+test_expect_success \
+    'change in branch B (addition and modification)' \
+    'git update-index --add LL &&
+     git update-index SS'
+mv TT TT-
+sed -e '/Branch B/s/word/WORD/g' <TT- >TT
+rm -f TT-
+test_expect_success \
+    'change in branch B (modification)' \
+    'git update-index TT'
+
+echo Branch B makes a file at DF. >DF
+test_expect_success \
+    'change in branch B (addition of a file to conflict with directory)' \
+    'git update-index --add DF'
+
+test_expect_success \
+    'recording branch B tree' \
+    'tree_B=$(git write-tree)'
+
+test_expect_success \
+    'keep contents of 3 trees for easy access' \
+    'rm -f .git/index &&
+     git read-tree $tree_O &&
+     mkdir .orig-O &&
+     git checkout-index --prefix=.orig-O/ -f -q -a &&
+     rm -f .git/index &&
+     git read-tree $tree_A &&
+     mkdir .orig-A &&
+     git checkout-index --prefix=.orig-A/ -f -q -a &&
+     rm -f .git/index &&
+     git read-tree $tree_B &&
+     mkdir .orig-B &&
+     git checkout-index --prefix=.orig-B/ -f -q -a'