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>

t/t0001-init.sh

@@ -167,9 +167,8 @@ test_expect_success 'reinit' '
 	) &&
 	test_i18ngrep "Initialized empty" again/out1 &&
 	test_i18ngrep "Reinitialized existing" again/out2 &&
-	>again/empty &&
-	test_i18ncmp again/empty again/err1 &&
-	test_i18ncmp again/empty again/err2
+	test_must_be_empty again/err1 &&
+	test_must_be_empty again/err2
 '
 test_expect_success 'init with --template' '

t/t0003-attributes.sh

@@ -208,9 +208,8 @@ test_expect_success 'attribute test: --all option' '
 '
 test_expect_success 'attribute test: --cached option' '
-	: >empty &&
 	git check-attr --cached --stdin --all <stdin-all | sort >actual &&
-	test_cmp empty actual &&
+	test_must_be_empty actual &&
 	git add .gitattributes a/.gitattributes a/b/.gitattributes &&
 	git check-attr --cached --stdin --all <stdin-all | sort >actual &&
 	test_cmp specified-all actual

t/t0030-stripspace.sh

@@ -320,22 +320,20 @@ test_expect_success \
 test_expect_success \
     'spaces with newline at end should be replaced with empty string' '
-    printf "" >expect &&
-
     echo | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     echo "$sss" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     echo "$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     echo "$sss$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     echo "$sss$sss$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual
+    test_must_be_empty actual
 '
 test_expect_success \
@@ -349,19 +347,17 @@ test_expect_success \
 test_expect_success \
     'spaces without newline at end should be replaced with empty string' '
-    printf "" >expect &&
-
     printf "" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     printf "$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     printf "$sss$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual &&
+    test_must_be_empty actual &&
     printf "$sss$sss$sss$sss" | git stripspace >actual &&
-    test_cmp expect actual
+    test_must_be_empty actual
 '
 test_expect_success \

t/t0040-parse-options.sh

@@ -286,11 +286,9 @@ test_expect_success 'OPT_CALLBACK() and OPT_BIT() work' '
 	test_cmp expect output
 '
->expect
-
 test_expect_success 'OPT_CALLBACK() and callback errors work' '
 	test_must_fail test-parse-options --no-length >output 2>output.err &&
-	test_i18ncmp expect output &&
+	test_must_be_empty output &&
 	test_must_be_empty output.err
 '

t/t0061-run-command.sh

@@ -11,7 +11,6 @@ cat >hello-script <<-EOF
 	#!$SHELL_PATH
 	cat hello-script
 EOF
->empty
 test_expect_success 'start_command reports ENOENT' '
 	test-tool run-command start-command-ENOENT ./does-not-exist
@@ -23,7 +22,7 @@ test_expect_success 'run_command can run a command' '
 	test-tool run-command run-command ./hello.sh >actual 2>err &&
 	test_cmp hello-script actual &&
-	test_cmp empty err
+	test_must_be_empty err
 '
 test_expect_success !MINGW 'run_command can run a script without a #! line' '
@@ -34,7 +33,7 @@ test_expect_success !MINGW 'run_command can run a script without a #! line' '
 	test-tool run-command run-command ./hello >actual 2>err &&
 	test_cmp hello-script actual &&
-	test_cmp empty err
+	test_must_be_empty err
 '
 test_expect_success 'run_command does not try to execute a directory' '
@@ -47,7 +46,7 @@ test_expect_success 'run_command does not try to execute a directory' '
 	PATH=$PWD/bin1:$PWD/bin2:$PATH \
 		test-tool run-command run-command greet >actual 2>err &&
 	test_cmp bin2/greet actual &&
-	test_cmp empty err
+	test_must_be_empty err
 '
 test_expect_success POSIXPERM 'run_command passes over non-executable file' '
@@ -64,7 +63,7 @@ test_expect_success POSIXPERM 'run_command passes over non-executable file' '
 	PATH=$PWD/bin1:$PWD/bin2:$PATH \
 		test-tool run-command run-command greet >actual 2>err &&
 	test_cmp bin2/greet actual &&
-	test_cmp empty err
+	test_must_be_empty err
 '
 test_expect_success POSIXPERM 'run_command reports EACCES' '

t/t1300-config.sh

@@ -346,12 +346,9 @@ test_expect_success 'working --list' '
 	git config --list > output &&
 	test_cmp expect output
 '
-cat > expect << EOF
-EOF
-
 test_expect_success '--list without repo produces empty output' '
 	git --git-dir=nonexistent config --list >output &&
-	test_cmp expect output
+	test_must_be_empty output
 '
 cat > expect << EOF

t/t1410-reflog.sh

@@ -290,9 +290,8 @@ test_expect_success 'stale dirs do not cause d/f conflicts (reflogs off)' '
 	# same as before, but we only create a reflog for "one" if
 	# it already exists, which it does not
 	git -c core.logallrefupdates=false branch one master &&
-	: >expect &&
 	git log -g --format="%gd %gs" one >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 # Triggering the bug detected by this test requires a newline to fall

t/t1411-reflog-show.sh

@@ -136,13 +136,12 @@ test_expect_success '--date magic does not override explicit @{0} syntax' '
 	test_cmp expect actual
 '
-: >expect
 test_expect_success 'empty reflog file' '
 	git branch empty &&
 	git reflog expire --expire=all refs/heads/empty &&
 	git log -g empty >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 # This guards against the alternative of showing the diffs vs. the

t/t1450-fsck.sh

@@ -16,8 +16,7 @@ test_expect_success setup '
 	git checkout HEAD^0 &&
 	test_commit B fileB two &&
 	git tag -d A B &&
-	git reflog expire --expire=now --all &&
-	>empty
+	git reflog expire --expire=now --all
 '
 test_expect_success 'loose objects borrowed from alternate are not missing' '
@@ -29,12 +28,12 @@ test_expect_success 'loose objects borrowed from alternate are not missing' '
 		test_commit C fileC one &&
 		git fsck --no-dangling >../actual 2>&1
 	) &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 test_expect_success 'HEAD is part of refs, valid objects appear valid' '
 	git fsck >actual 2>&1 &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 # Corruption tests follow.  Make sure to remove all traces of the
@@ -346,12 +345,12 @@ test_expect_success 'tag with NUL in header' '
 test_expect_success 'cleaned up' '
 	git fsck >actual 2>&1 &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 test_expect_success 'rev-list --verify-objects' '
 	git rev-list --verify-objects --all >/dev/null 2>out &&
-	test_cmp empty out
+	test_must_be_empty out
 '
 test_expect_success 'rev-list --verify-objects with bad sha1' '

t/t1600-index.sh

@@ -41,8 +41,7 @@ test_expect_success 'no warning with bogus GIT_INDEX_VERSION and existing index'
 		GIT_INDEX_VERSION=1 &&
 		export GIT_INDEX_VERSION &&
 		git add a 2>actual.err &&
-		>expect.err &&
-		test_i18ncmp expect.err actual.err
+		test_must_be_empty actual.err
 	)
 '

t/t1700-split-index.sh

@@ -143,9 +143,7 @@ test_expect_success 'remove file not in base index' '
 test_expect_success 'remove file in base index' '
 	git update-index --force-remove one &&
 	git ls-files --stage >ls-files.actual &&
-	cat >ls-files.expect <<-EOF &&
-	EOF
-	test_cmp ls-files.expect ls-files.actual &&
+	test_must_be_empty ls-files.actual &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
 	cat >expect <<-EOF &&

t/t2200-add-update.sh

@@ -88,9 +88,8 @@ test_expect_success 'non-qualified update in subdir updates from the root' '
 		echo even more >>sub2 &&
 		git add -u
 	) &&
-	: >expect &&
 	git diff-files --name-only >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 test_expect_success 'replace a file with a symlink' '

t/t2203-add-intent.sh

@@ -195,8 +195,7 @@ test_expect_success 'rename detection finds the right names' '
 		test_cmp expected.4 actual.4 &&
 		git diff --cached --stat >actual.5 &&
-		: >expected.5 &&
-		test_cmp expected.5 actual.5
+		test_must_be_empty actual.5
 	)
 '
@@ -241,8 +240,7 @@ test_expect_success 'diff-files/diff-cached shows ita as new/not-new files' '
 	echo " create mode 100644 new-ita" >expected &&
 	test_cmp expected actual &&
 	git diff --cached --summary >actual2 &&
-	: >expected2 &&
-	test_cmp expected2 actual2
+	test_must_be_empty actual2
 '

t/t3001-ls-files-others-exclude.sh

@@ -277,9 +277,8 @@ test_expect_success 'hide empty ignored sub-directory with --no-empty-directory'
 '
 test_expect_success 'pattern matches prefix completely' '
-	: >expect &&
 	git ls-files -i -o --exclude "/three/a.3[abc]" >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 test_expect_success 'ls-files with "**" patterns' '
@@ -295,9 +294,8 @@ EOF
 test_expect_success 'ls-files with "**" patterns and no slashes' '
-	: >expect &&
 	git ls-files -o -i --exclude "one**a.1" >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 test_done

t/t3004-ls-files-basic.sh

@@ -8,16 +8,14 @@ command-line arguments.
 . ./test-lib.sh
->empty
-
 test_expect_success 'ls-files in empty repository' '
 	git ls-files >actual &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 test_expect_success 'ls-files with nonexistent path' '
 	git ls-files doesnotexist >actual &&
-	test_cmp empty actual
+	test_must_be_empty actual
 '
 test_expect_success 'ls-files with nonsense option' '

t/t3035-merge-sparse.sh

@@ -17,7 +17,6 @@ test_commit_this () {
 }
 test_expect_success 'setup' '
-	: >empty &&
 	test_file checked-out init &&
 	test_file modify_delete modify_delete_init &&
 	test_commit_this init &&
@@ -38,7 +37,7 @@ test_expect_success 'reset --hard works after the conflict' '
 test_expect_success 'is reset properly' '
 	git status --porcelain -- modify_delete >out &&
-	test_cmp empty out &&
+	test_must_be_empty out &&
 	test_path_is_missing modify_delete
 '
@@ -52,7 +51,7 @@ test_expect_success 'Merge abort works after the conflict' '
 test_expect_success 'is aborted properly' '
 	git status --porcelain -- modify_delete >out &&
-	test_cmp empty out &&
+	test_must_be_empty out &&
 	test_path_is_missing modify_delete
 '

t/t3301-notes.sh

@@ -481,10 +481,8 @@ test_expect_success 'list specific note with "git notes list <object>"' '
 '
 test_expect_success 'listing non-existing notes fails' '
-	cat >expect <<-EOF &&
-	EOF
 	test_must_fail git notes list HEAD >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 test_expect_success 'append to existing note with "git notes append"' '

t/t3404-rebase-interactive.sh

@@ -787,16 +787,15 @@ test_expect_success 'always cherry-pick with --no-ff' '
 	git tag original-no-ff-branch &&
 	set_fake_editor &&
 	git rebase -i --no-ff A &&
-	touch empty &&
 	for p in 0 1 2
 	do
 		test ! $(git rev-parse HEAD~$p) = $(git rev-parse original-no-ff-branch~$p) &&
 		git diff HEAD~$p original-no-ff-branch~$p > out &&
-		test_cmp empty out
+		test_must_be_empty out
 	done &&
 	test $(git rev-parse HEAD~3) = $(git rev-parse original-no-ff-branch~3) &&
 	git diff HEAD~3 original-no-ff-branch~3 > out &&
-	test_cmp empty out
+	test_must_be_empty out
 '
 test_expect_success 'set up commits with funny messages' '

t/t4015-diff-whitespace.sh

@@ -776,8 +776,6 @@ test_expect_success 'checkdiff allows new blank lines' '
 	git diff --check
 '
-cat <<EOF >expect
-EOF
 test_expect_success 'whitespace-only changes not reported' '
 	git reset --hard &&
 	echo >x "hello world" &&
@@ -785,7 +783,7 @@ test_expect_success 'whitespace-only changes not reported' '
 	git commit -m "hello 1" &&
 	echo >x "hello  world" &&
 	git diff -b >actual &&
-	test_cmp expect actual
+	test_must_be_empty actual
 '
 cat <<EOF >expect

t/t4027-diff-submodule.sh

@@ -239,10 +239,9 @@ test_expect_success 'git diff between submodule commits [.gitmodules]' '
 '
 test_expect_success 'git diff (empty submodule dir)' '
-	: >empty &&
 	rm -rf sub/* sub/.git &&
 	git diff > actual.empty &&
-	test_cmp empty actual.empty
+	test_must_be_empty actual.empty
 '
 test_expect_success 'conflicted submodule setup' '