Merge branch 'en/dirty-merge-fixes'

The recursive merge strategy did not properly ensure there was no
change between HEAD and the index before performing its operation,
which has been corrected.

* en/dirty-merge-fixes:
  merge: fix misleading pre-merge check documentation
  merge-recursive: enforce rule that index matches head before merging
  t6044: add more testcases with staged changes before a merge is invoked
  merge-recursive: fix assumption that head tree being merged is HEAD
  merge-recursive: make sure when we say we abort that we actually abort
  t6044: add a testcase for index matching head, when head doesn't match HEAD
  t6044: verify that merges expected to abort actually abort
  index_has_changes(): avoid assuming operating on the_index
  read-cache.c: move index_has_changes() from merge.c

3 files changed, 60 insertions, 129 deletions

diff --git a/t/t6044-merge-unrelated-index-changes.sh b/t/t6044-merge-unrelated-index-changes.sh
index 23b86fb977..5e3779ebc9 100755
--- a/t/t6044-merge-unrelated-index-changes.sh
+++ b/t/t6044-merge-unrelated-index-changes.sh
@@ -82,7 +82,8 @@ test_expect_success 'ff update, important file modified' '
 	touch subdir/e &&
 	git add subdir/e &&
 
-	test_must_fail git merge E^0
+	test_must_fail git merge E^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'resolve, trivial' '
@@ -91,7 +92,8 @@ test_expect_success 'resolve, trivial' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s resolve C^0
+	test_must_fail git merge -s resolve C^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'resolve, non-trivial' '
@@ -100,7 +102,8 @@ test_expect_success 'resolve, non-trivial' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s resolve D^0
+	test_must_fail git merge -s resolve D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'recursive' '
@@ -109,7 +112,8 @@ test_expect_success 'recursive' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s recursive C^0
+	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' '
@@ -118,7 +122,45 @@ test_expect_success 'recursive, when merge branch matches merge base' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s recursive F^0
+	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' '
@@ -127,7 +169,8 @@ test_expect_success 'octopus, unrelated file touched' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge C^0 D^0
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'octopus, related file removed' '
@@ -136,7 +179,8 @@ test_expect_success 'octopus, related file removed' '
 
 	git rm b &&
 
-	test_must_fail git merge C^0 D^0
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'octopus, related file modified' '
@@ -145,7 +189,8 @@ test_expect_success 'octopus, related file modified' '
 
 	echo 12 >>a && git add a &&
 
-	test_must_fail git merge C^0 D^0
+	test_must_fail git merge C^0 D^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'ours' '
@@ -154,7 +199,8 @@ test_expect_success 'ours' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s ours C^0
+	test_must_fail git merge -s ours C^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_expect_success 'subtree' '
@@ -163,7 +209,8 @@ test_expect_success 'subtree' '
 
 	touch random_file && git add random_file &&
 
-	test_must_fail git merge -s subtree E^0
+	test_must_fail git merge -s subtree E^0 &&
+	test_path_is_missing .git/MERGE_HEAD
 '
 
 test_done
diff --git a/t/t7504-commit-msg-hook.sh b/t/t7504-commit-msg-hook.sh
index 302a3a2082..31b9c6a2c1 100755
--- a/t/t7504-commit-msg-hook.sh
+++ b/t/t7504-commit-msg-hook.sh
@@ -157,6 +157,7 @@ test_expect_success 'merge bypasses failing hook with --no-verify' '
 	test_when_finished "git branch -D newbranch" &&
 	test_when_finished "git checkout -f master" &&
 	git checkout --orphan newbranch &&
+	git rm -f file &&
 	: >file2 &&
 	git add file2 &&
 	git commit --no-verify file2 -m in-side-branch &&
@@ -168,7 +169,7 @@ test_expect_success 'merge bypasses failing hook with --no-verify' '
 chmod -x "$HOOK"
 test_expect_success POSIXPERM 'with non-executable hook' '
 
-	echo "content" >> file &&
+	echo "content" >file &&
 	git add file &&
 	git commit -m "content"
 
@@ -249,6 +250,7 @@ test_expect_success 'hook called in git-merge picks up commit message' '
 	test_when_finished "git branch -D newbranch" &&
 	test_when_finished "git checkout -f master" &&
 	git checkout --orphan newbranch &&
+	git rm -f file &&
 	: >file2 &&
 	git add file2 &&
 	git commit --no-verify file2 -m in-side-branch &&
diff --git a/t/t7611-merge-abort.sh b/t/t7611-merge-abort.sh
index 7b4798e8e4..7c84a518aa 100755
--- a/t/t7611-merge-abort.sh
+++ b/t/t7611-merge-abort.sh
@@ -187,31 +187,6 @@ test_expect_success 'Fail clean merge with matching dirty worktree' '
 	test_cmp expect actual
 '
 
-test_expect_success 'Abort clean merge with matching dirty index' '
-	git add bar &&
-	git diff --staged > expect &&
-	git merge --no-commit clean_branch &&
-	test -f .git/MERGE_HEAD &&
-	### When aborting the merge, git will discard all staged changes,
-	### including those that were staged pre-merge. In other words,
-	### --abort will LOSE any staged changes (the staged changes that
-	### are lost must match the merge result, or the merge would not
-	### have been allowed to start). Change expectations accordingly:
-	rm expect &&
-	touch expect &&
-	# Abort merge
-	git merge --abort &&
-	test ! -f .git/MERGE_HEAD &&
-	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
-	git diff --staged > actual &&
-	test_cmp expect actual &&
-	test -z "$(git diff)"
-'
-
-test_expect_success 'Reset worktree changes' '
-	git reset --hard "$pre_merge_head"
-'
-
 test_expect_success 'Fail conflicting merge with matching dirty worktree' '
 	echo barf > bar &&
 	git diff > expect &&
@@ -223,97 +198,4 @@ test_expect_success 'Fail conflicting merge with matching dirty worktree' '
 	test_cmp expect actual
 '
 
-test_expect_success 'Abort conflicting merge with matching dirty index' '
-	git add bar &&
-	git diff --staged > expect &&
-	test_must_fail git merge conflict_branch &&
-	test -f .git/MERGE_HEAD &&
-	### When aborting the merge, git will discard all staged changes,
-	### including those that were staged pre-merge. In other words,
-	### --abort will LOSE any staged changes (the staged changes that
-	### are lost must match the merge result, or the merge would not
-	### have been allowed to start). Change expectations accordingly:
-	rm expect &&
-	touch expect &&
-	# Abort merge
-	git merge --abort &&
-	test ! -f .git/MERGE_HEAD &&
-	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
-	git diff --staged > actual &&
-	test_cmp expect actual &&
-	test -z "$(git diff)"
-'
-
-test_expect_success 'Reset worktree changes' '
-	git reset --hard "$pre_merge_head"
-'
-
-test_expect_success 'Abort merge with pre- and post-merge worktree changes' '
-	# Pre-merge worktree changes
-	echo xyzzy > foo &&
-	echo barf > bar &&
-	git add bar &&
-	git diff > expect &&
-	git diff --staged > expect-staged &&
-	# Perform merge
-	test_must_fail git merge conflict_branch &&
-	test -f .git/MERGE_HEAD &&
-	# Post-merge worktree changes
-	echo yzxxz > foo &&
-	echo blech > baz &&
-	### When aborting the merge, git will discard staged changes (bar)
-	### and unmerged changes (baz). Other changes that are neither
-	### staged nor marked as unmerged (foo), will be preserved. For
-	### these changed, git cannot tell pre-merge changes apart from
-	### post-merge changes, so the post-merge changes will be
-	### preserved. Change expectations accordingly:
-	git diff -- foo > expect &&
-	rm expect-staged &&
-	touch expect-staged &&
-	# Abort merge
-	git merge --abort &&
-	test ! -f .git/MERGE_HEAD &&
-	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
-	git diff > actual &&
-	test_cmp expect actual &&
-	git diff --staged > actual-staged &&
-	test_cmp expect-staged actual-staged
-'
-
-test_expect_success 'Reset worktree changes' '
-	git reset --hard "$pre_merge_head"
-'
-
-test_expect_success 'Abort merge with pre- and post-merge index changes' '
-	# Pre-merge worktree changes
-	echo xyzzy > foo &&
-	echo barf > bar &&
-	git add bar &&
-	git diff > expect &&
-	git diff --staged > expect-staged &&
-	# Perform merge
-	test_must_fail git merge conflict_branch &&
-	test -f .git/MERGE_HEAD &&
-	# Post-merge worktree changes
-	echo yzxxz > foo &&
-	echo blech > baz &&
-	git add foo bar &&
-	### When aborting the merge, git will discard all staged changes
-	### (foo, bar and baz), and no changes will be preserved. Whether
-	### the changes were staged pre- or post-merge does not matter
-	### (except for not preventing starting the merge).
-	### Change expectations accordingly:
-	rm expect expect-staged &&
-	touch expect &&
-	touch expect-staged &&
-	# Abort merge
-	git merge --abort &&
-	test ! -f .git/MERGE_HEAD &&
-	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
-	git diff > actual &&
-	test_cmp expect actual &&
-	git diff --staged > actual-staged &&
-	test_cmp expect-staged actual-staged
-'
-
 test_done