Add more checkout tests

If you have local changes that don't conflict with the
branch-switching changes, these should be kept, not cause errors even
without -m, and be reported afterwards in name-status format.

With -m, the changes carried across should be listed as well. And, for
now, include the merge-recursive output from this process.

Also test the detatched head message in at least one case.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7201-co.sh

@@ -20,6 +20,8 @@ Test switching across them.
 
 . ./test-lib.sh
 
+test_tick
+
 fill () {
 	for i
 	do
@@ -30,9 +32,10 @@ fill () {
 
 test_expect_success setup '
 
+	fill x y z > same &&
 	fill 1 2 3 4 5 6 7 8 >one &&
 	fill a b c d e >two &&
-	git add one two &&
+	git add same one two &&
 	git commit -m "Initial A one, A two" &&
 
 	git checkout -b renamer &&
@@ -74,16 +77,44 @@ test_expect_success "checkout with dirty tree without -m" '
 
 '
 
+test_expect_success "checkout with unrelated dirty tree without -m" '
+
+	git checkout -f master &&
+	fill 0 1 2 3 4 5 6 7 8 >same &&
+	cp same kept
+	git checkout side >messages &&
+	git diff same kept
+	(cat > messages.expect <<EOF
+M	same
+EOF
+) &&
+	touch messages.expect &&
+	git diff messages.expect messages
+'
+
 test_expect_success "checkout -m with dirty tree" '
 
 	git checkout -f master &&
 	git clean -f &&
 
 	fill 0 1 2 3 4 5 6 7 8 >one &&
-	git checkout -m side &&
+	git checkout -m side > messages &&
 
 	test "$(git symbolic-ref HEAD)" = "refs/heads/side" &&
 
+	(cat >expect.messages <<EOF
+Merging side with local
+Merging:
+ab76817 Side M one, D two, A three
+virtual local
+found 1 common ancestor(s):
+7329388 Initial A one, A two
+Auto-merged one
+M	one
+EOF
+) &&
+	git diff expect.messages messages &&
+
 	fill "M	one" "A	three" "D	two" >expect.master &&
 	git diff --name-status master >current.master &&
 	diff expect.master current.master &&
@@ -145,7 +176,16 @@ test_expect_success 'checkout -m with merge conflict' '
 test_expect_success 'checkout to detach HEAD' '
 
 	git checkout -f renamer && git clean -f &&
-	git checkout renamer^ &&
+	git checkout renamer^ 2>messages &&
+	(cat >messages.expect <<EOF
+Note: moving to "renamer^" which isn'"'"'t a local branch
+If you want to create a new branch from this checkout, you may do so
+(now or later) by using -b with the checkout command again. Example:
+  git checkout -b <new_branch_name>
+HEAD is now at 7329388... Initial A one, A two
+EOF
+) &&
+	git diff messages.expect messages &&
 	H=$(git rev-parse --verify HEAD) &&
 	M=$(git show-ref -s --verify refs/heads/master) &&
 	test "z$H" = "z$M" &&