unpack-trees: don't update files with CE_WT_REMOVE set

Don't update files in the worktree from cache entries which are
flagged with CE_WT_REMOVE.

When a user does a sparse checkout, git removes files that are
marked with CE_WT_REMOVE (because they are out-of-scope for the
sparse checkout). If those files are also marked CE_UPDATE (for
instance, because they differ in the branch that is being checked
out and the outgoing branch), git would previously recreate them.
This patch prevents them from being recreated.

These erroneously-created files would also interfere with merges,
causing pre-merge revisions of out-of-scope files to appear in the
worktree.

apply_sparse_checkout() is the function where all "action"
manipulation (add, delete, update files..) for sparse checkout
occurs; it should not ask to delete and update both at the same
time.

Signed-off-by: Anatole Shaw <git-devel@omni.poc.net>
Signed-off-by: David Turner <dturner@twopensource.com>
Helped-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1090-sparse-checkout-scope.sh

@@ -0,0 +1,52 @@
+#!/bin/sh
+
+test_description='sparse checkout scope tests'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo "initial" >a &&
+	echo "initial" >b &&
+	echo "initial" >c &&
+	git add a b c &&
+	git commit -m "initial commit"
+'
+
+test_expect_success 'create feature branch' '
+	git checkout -b feature &&
+	echo "modified" >b &&
+	echo "modified" >c &&
+	git add b c &&
+	git commit -m "modification"
+'
+
+test_expect_success 'perform sparse checkout of master' '
+	git config --local --bool core.sparsecheckout true &&
+	echo "!/*" >.git/info/sparse-checkout &&
+	echo "/a" >>.git/info/sparse-checkout &&
+	echo "/c" >>.git/info/sparse-checkout &&
+	git checkout master &&
+	test_path_is_file a &&
+	test_path_is_missing b &&
+	test_path_is_file c
+'
+
+test_expect_success 'merge feature branch into sparse checkout of master' '
+	git merge feature &&
+	test_path_is_file a &&
+	test_path_is_missing b &&
+	test_path_is_file c &&
+	test "$(cat c)" = "modified"
+'
+
+test_expect_success 'return to full checkout of master' '
+	git checkout feature &&
+	echo "/*" >.git/info/sparse-checkout &&
+	git checkout master &&
+	test_path_is_file a &&
+	test_path_is_file b &&
+	test_path_is_file c &&
+	test "$(cat b)" = "modified"
+'
+
+test_done

unpack-trees.c

@@ -227,6 +227,9 @@ static int check_updates(struct unpack_trees_options *o)
 		struct cache_entry *ce = index->cache[i];
 
 		if (ce->ce_flags & CE_UPDATE) {
+			if (ce->ce_flags & CE_WT_REMOVE)
+				die("BUG: both update and delete flags are set on %s",
+				    ce->name);
 			display_progress(progress, ++cnt);
 			ce->ce_flags &= ~CE_UPDATE;
 			if (o->update && !o->dry_run) {
@@ -290,6 +293,7 @@ static int apply_sparse_checkout(struct cache_entry *ce, struct unpack_trees_opt
 		if (!(ce->ce_flags & CE_UPDATE) && verify_uptodate_sparse(ce, o))
 			return -1;
 		ce->ce_flags |= CE_WT_REMOVE;
+		ce->ce_flags &= ~CE_UPDATE;
 	}
 	if (was_skip_worktree && !ce_skip_worktree(ce)) {
 		if (verify_absent_sparse(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))