Merge branch 'hv/submodule-find-ff-merge'

* hv/submodule-find-ff-merge:
  Implement automatic fast-forward merge for submodules
  setup_revisions(): Allow walking history in a submodule
  Teach ref iteration module about submodules

Conflicts:
	submodule.c

1 files changed, 122 insertions, 6 deletions

diff --git a/t/t7405-submodule-merge.sh b/t/t7405-submodule-merge.sh
index 4a7b893..6ec559d 100755
--- a/t/t7405-submodule-merge.sh
+++ b/t/t7405-submodule-merge.sh
@@ -54,13 +54,129 @@ test_expect_success setup '
 	git merge -s ours a
 '
 
-test_expect_success 'merging with modify/modify conflict' '
+# History setup
+#
+#      b
+#    /   \
+#   a     d
+#    \   /
+#      c
+#
+# a in the main repository records to sub-a in the submodule and
+# analogous b and c. d should be automatically found by merging c into
+# b in the main repository.
+test_expect_success 'setup for merge search' '
+	mkdir merge-search &&
+	cd merge-search &&
+	git init &&
+	mkdir sub &&
+	(cd sub &&
+	 git init &&
+	 echo "file-a" > file-a &&
+	 git add file-a &&
+	 git commit -m "sub-a" &&
+	 git branch sub-a) &&
+	git add sub &&
+	git commit -m "a" &&
+	git branch a &&
+
+	git checkout -b b &&
+	(cd sub &&
+	 git checkout -b sub-b &&
+	 echo "file-b" > file-b &&
+	 git add file-b &&
+	 git commit -m "sub-b") &&
+	git commit -a -m "b" &&
+
+	git checkout -b c a &&
+	(cd sub &&
+	 git checkout -b sub-c sub-a &&
+	 echo "file-c" > file-c &&
+	 git add file-c &&
+	 git commit -m "sub-c") &&
+	git commit -a -m "c" &&
+
+	git checkout -b d a &&
+	(cd sub &&
+	 git checkout -b sub-d sub-b &&
+	 git merge sub-c) &&
+	git commit -a -m "d" &&
+	git branch test b &&
+	cd ..
+'
+
+test_expect_success 'merge with one side as a fast-forward of the other' '
+	(cd merge-search &&
+	 git checkout -b test-forward b &&
+	 git merge d &&
+	 git ls-tree test-forward sub | cut -f1 | cut -f3 -d" " > actual &&
+	 (cd sub &&
+	  git rev-parse sub-d > ../expect) &&
+	 test_cmp actual expect)
+'
+
+test_expect_success 'merging should conflict for non fast-forward' '
+	(cd merge-search &&
+	 git checkout -b test-nonforward b &&
+	 (cd sub &&
+	  git rev-parse sub-d > ../expect) &&
+	 test_must_fail git merge c 2> actual  &&
+	 grep $(cat expect) actual > /dev/null &&
+	 git reset --hard)
+'
+
+test_expect_success 'merging should fail for ambiguous common parent' '
+	cd merge-search &&
+	git checkout -b test-ambiguous b &&
+	(cd sub &&
+	 git checkout -b ambiguous sub-b &&
+	 git merge sub-c &&
+	 git rev-parse sub-d > ../expect1 &&
+	 git rev-parse ambiguous > ../expect2) &&
+	test_must_fail git merge c 2> actual &&
+	grep $(cat expect1) actual > /dev/null &&
+	grep $(cat expect2) actual > /dev/null &&
+	git reset --hard &&
+	cd ..
+'
+
+# in a situation like this
+#
+# submodule tree:
+#
+#    sub-a --- sub-b --- sub-d
+#
+# main tree:
+#
+#    e (sub-a)
+#   /
+#  bb (sub-b)
+#   \
+#    f (sub-d)
+#
+# A merge between e and f should fail because one of the submodule
+# commits (sub-a) does not descend from the submodule merge-base (sub-b).
+#
+test_expect_success 'merging should fail for changes that are backwards' '
+	cd merge-search &&
+	git checkout -b bb a &&
+	(cd sub &&
+	 git checkout sub-b) &&
+	git commit -a -m "bb" &&
+
+	git checkout -b e bb &&
+	(cd sub &&
+	 git checkout sub-a) &&
+	git commit -a -m "e" &&
+
+	git checkout -b f bb &&
+	(cd sub &&
+	 git checkout sub-d) &&
+	git commit -a -m "f" &&
 
-	git checkout -b test1 a &&
-	test_must_fail git merge b &&
-	test -f .git/MERGE_MSG &&
-	git diff &&
-	test -n "$(git ls-files -u)"
+	git checkout -b test-backward e &&
+	test_must_fail git merge f &&
+	cd ..
 '
 
 test_expect_success 'merging with a modify/modify conflict between merge bases' '