tests: use 'test_must_be_empty' instead of 'test_cmp <empty> <out>'

Using 'test_must_be_empty' is shorter and more idiomatic than

  >empty &&
  test_cmp empty out

as it saves the creation of an empty file.  Furthermore, sometimes the
expected empty file doesn't have such a descriptive name like 'empty',
and its creation is far away from the place where it's finally used
for comparison (e.g. in 't7600-merge.sh', where two expected empty
files are created in the 'setup' test, but are used only about 500
lines later).

These cases were found by instrumenting 'test_cmp' to error out the
test script when it's used to compare empty files, and then converted
manually.

Note that even after this patch there still remain a lot of cases
where we use 'test_cmp' to check empty files:

  - Sometimes the expected output is not hard-coded in the test, but
    'test_cmp' is used to ensure that two similar git commands produce
    the same output, and that output happens to be empty, e.g. the
    test 'submodule update --merge  - ignores --merge  for new
    submodules' in 't7406-submodule-update.sh'.

  - Repetitive common tasks, including preparing the expected results
    and running 'test_cmp', are often extracted into a helper
    function, and some of this helper's callsites expect no output.

  - For the same reason as above, the whole 'test_expect_success'
    block is within a helper function, e.g. in 't3070-wildmatch.sh'.

  - Or 'test_cmp' is invoked in a loop, e.g. the test 'cvs update
    (-p)' in 't9400-git-cvsserver-server.sh'.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 20 deletions

diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 42d5354c2a..c82c8f5f72 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -217,9 +217,8 @@ do
 	'
 
 	test_expect_success "grep -w $L (w)" '
-		: >expected &&
 		test_must_fail git grep -n -w -e "^w" $H >actual &&
-		test_cmp expected actual
+		test_must_be_empty actual
 	'
 
 	test_expect_success "grep -w $L (x)" '
@@ -239,26 +238,24 @@ do
 	'
 
 	test_expect_success "grep -w $L (y-2)" '
-		: >expected &&
 		if git grep -n -w -e "^y y" $H >actual
 		then
 			echo should not have matched
 			cat actual
 			false
 		else
-			test_cmp expected actual
+			test_must_be_empty actual
 		fi
 	'
 
 	test_expect_success "grep -w $L (z)" '
-		: >expected &&
 		if git grep -n -w -e "^z" $H >actual
 		then
 			echo should not have matched
 			cat actual
 			false
 		else
-			test_cmp expected actual
+			test_must_be_empty actual
 		fi
 	'
 
@@ -604,11 +601,10 @@ z:zzz
 EOF
 
 test_expect_success 'grep -q, silently report matches' '
-	>empty &&
 	git grep -q mmap >actual &&
-	test_cmp empty actual &&
+	test_must_be_empty actual &&
 	test_must_fail git grep -q qfwfq >actual &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 
 test_expect_success 'grep -C1 hunk mark between files' '
@@ -701,8 +697,7 @@ test_expect_success 'log grep (9)' '
 
 test_expect_success 'log grep (9)' '
 	git log -g --grep-reflog="commit: third" --author="non-existent" --pretty=tformat:%s >actual &&
-	: >expect &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 
 test_expect_success 'log --grep-reflog can only be used under -g' '
@@ -792,15 +787,13 @@ test_expect_success 'log --all-match --grep --grep --author takes intersection'
 '
 
 test_expect_success 'log --author does not search in timestamp' '
-	: >expect &&
 	git log --author="$GIT_AUTHOR_DATE" >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 
 test_expect_success 'log --committer does not search in timestamp' '
-	: >expect &&
 	git log --committer="$GIT_COMMITTER_DATE" >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 
 test_expect_success 'grep with CE_VALID file' '
@@ -1051,13 +1044,12 @@ test_expect_success 'inside git repository but with --no-index' '
 		echo ".gitignore:.*o*" &&
 		cat is/expect.unignored
 	} >is/expect.full &&
-	: >is/expect.empty &&
 	echo file2:world >is/expect.sub &&
 	(
 		cd is/git &&
 		git init &&
 		test_must_fail git grep o >../actual.full &&
-		test_cmp ../expect.empty ../actual.full &&
+		test_must_be_empty ../actual.full &&
 
 		git grep --untracked o >../actual.unignored &&
 		test_cmp ../expect.unignored ../actual.unignored &&
@@ -1070,7 +1062,7 @@ test_expect_success 'inside git repository but with --no-index' '
 
 		cd sub &&
 		test_must_fail git grep o >../../actual.sub &&
-		test_cmp ../../expect.empty ../../actual.sub &&
+		test_must_be_empty ../../actual.sub &&
 
 		git grep --no-index o >../../actual.sub &&
 		test_cmp ../../expect.sub ../../actual.sub &&
@@ -1236,10 +1228,9 @@ test_expect_success !PCRE 'grep -P pattern errors without PCRE' '
 '
 
 test_expect_success 'grep pattern with grep.extendedRegexp=true' '
-	>empty &&
 	test_must_fail git -c grep.extendedregexp=true \
 		grep "\p{Ps}.*?\p{Pe}" hello.c >actual &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 
 test_expect_success PCRE 'grep -P pattern with grep.extendedRegexp=true' '