t4150 (am): futureproof against failing tests

Most tests in t4150 begin by navigating to a sane state and
applying some patch:

	git checkout first &&
	git am patch1

If a previous test left behind unmerged files or a .git/rebase-apply
directory, they are untouched and the test fails, causing later tests
to fail, too.  This is not a problem in practice because none of the
tests leave a mess behind.

But as a futureproofing measure, it is still best to avoid the problem
and clean up at the start of each test.  In particular, this
simplifies the process of adding new tests that are known to fail.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4150-am.sh

@@ -122,6 +122,8 @@ test_expect_success setup '
 '
 
 test_expect_success 'am applies patch correctly' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	git am <patch1 &&
@@ -132,6 +134,8 @@ test_expect_success 'am applies patch correctly' '
 '
 
 test_expect_success 'am applies patch e-mail not in a mbox' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	git am patch1.eml &&
 	! test -d .git/rebase-apply &&
@@ -141,6 +145,8 @@ test_expect_success 'am applies patch e-mail not in a mbox' '
 '
 
 test_expect_success 'am applies patch e-mail not in a mbox with CRLF' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	git am patch1-crlf.eml &&
 	! test -d .git/rebase-apply &&
@@ -165,6 +171,8 @@ compare () {
 
 test_expect_success 'am changes committer and keeps author' '
 	test_tick &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	git am patch2 &&
 	! test -d .git/rebase-apply &&
@@ -178,6 +186,8 @@ test_expect_success 'am changes committer and keeps author' '
 '
 
 test_expect_success 'am --signoff adds Signed-off-by: line' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout -b master2 first &&
 	git am --signoff <patch2 &&
 	printf "%s\n" "$signoff" >expected &&
@@ -198,6 +208,8 @@ test_expect_success 'am stays in branch' '
 test_expect_success 'am --signoff does not add Signed-off-by: line if already there' '
 	git format-patch --stdout HEAD^ >patch3 &&
 	sed -e "/^Subject/ s,\[PATCH,Re: Re: Re: & 1/5 v2," patch3 >patch4
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout HEAD^ &&
 	git am --signoff patch4 &&
 	git cat-file commit HEAD >actual &&
@@ -211,6 +223,8 @@ test_expect_success 'am without --keep removes Re: and [PATCH] stuff' '
 '
 
 test_expect_success 'am --keep really keeps the subject' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout HEAD^ &&
 	git am --keep patch4 &&
 	! test -d .git/rebase-apply &&
@@ -219,6 +233,8 @@ test_expect_success 'am --keep really keeps the subject' '
 '
 
 test_expect_success 'am -3 falls back to 3-way merge' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout -b lorem2 master2 &&
 	sed -n -e "3,\$p" msg >file &&
 	head -n 9 msg >>file &&
@@ -231,6 +247,7 @@ test_expect_success 'am -3 falls back to 3-way merge' '
 '
 
 test_expect_success 'am -3 -q is quiet' '
+	rm -fr .git/rebase-apply &&
 	git reset master2 --hard &&
 	sed -n -e "3,\$p" msg >file &&
 	head -n 9 msg >>file &&
@@ -242,6 +259,8 @@ test_expect_success 'am -3 -q is quiet' '
 '
 
 test_expect_success 'am pauses on conflict' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout lorem2^^ &&
 	test_must_fail git am lorem-move.patch &&
 	test -d .git/rebase-apply
@@ -257,6 +276,8 @@ test_expect_success 'am --skip works' '
 
 test_expect_success 'am --resolved works' '
 	echo goodbye >expected &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout lorem2^^ &&
 	test_must_fail git am lorem-move.patch &&
 	test -d .git/rebase-apply &&
@@ -268,18 +289,25 @@ test_expect_success 'am --resolved works' '
 '
 
 test_expect_success 'am takes patches from a Pine mailbox' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	cat pine patch1 | git am &&
 	! test -d .git/rebase-apply &&
 	git diff --exit-code master^..HEAD
 '
 
 test_expect_success 'am fails on mail without patch' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	test_must_fail git am <failmail &&
-	rm -r .git/rebase-apply/
+	git am --abort &&
+	! test -d .git/rebase-apply
 '
 
 test_expect_success 'am fails on empty patch' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	echo "---" >>failmail &&
 	test_must_fail git am <failmail &&
 	git am --skip &&
@@ -288,6 +316,8 @@ test_expect_success 'am fails on empty patch' '
 
 test_expect_success 'am works from stdin in subdirectory' '
 	rm -fr subdir &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	(
 		mkdir -p subdir &&
@@ -299,6 +329,8 @@ test_expect_success 'am works from stdin in subdirectory' '
 
 test_expect_success 'am works from file (relative path given) in subdirectory' '
 	rm -fr subdir &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	(
 		mkdir -p subdir &&
@@ -310,6 +342,8 @@ test_expect_success 'am works from file (relative path given) in subdirectory' '
 
 test_expect_success 'am works from file (absolute path given) in subdirectory' '
 	rm -fr subdir &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	P=$(pwd) &&
 	(
@@ -321,6 +355,8 @@ test_expect_success 'am works from file (absolute path given) in subdirectory' '
 '
 
 test_expect_success 'am --committer-date-is-author-date' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	git am --committer-date-is-author-date patch1 &&
@@ -331,6 +367,8 @@ test_expect_success 'am --committer-date-is-author-date' '
 '
 
 test_expect_success 'am without --committer-date-is-author-date' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	git am patch1 &&
@@ -345,6 +383,8 @@ test_expect_success 'am without --committer-date-is-author-date' '
 # by test_tick that uses -0700 timezone; if this feature does not
 # work, we will see that instead of +0000.
 test_expect_success 'am --ignore-date' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	git am --ignore-date patch1 &&
@@ -355,6 +395,8 @@ test_expect_success 'am --ignore-date' '
 
 test_expect_success 'am into an unborn branch' '
 	git rev-parse first^{tree} >expected &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	rm -fr subdir &&
 	mkdir subdir &&
 	git format-patch --numbered-files -o subdir -1 first &&
@@ -371,6 +413,8 @@ test_expect_success 'am into an unborn branch' '
 '
 
 test_expect_success 'am newline in subject' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	sed -e "s/second/second \\\n foo/" patch1 >patchnl &&
@@ -379,6 +423,8 @@ test_expect_success 'am newline in subject' '
 '
 
 test_expect_success 'am -q is quiet' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
 	git checkout first &&
 	test_tick &&
 	git am -q <patch1 >output.out 2>&1 &&