test-lib-functions: remove bug-inducing "diagnostics" helper param

Remove the optional "diagnostics" parameter of the
test_path_is_{file,dir,missing} functions.

We have a lot of uses of these functions, but the only legitimate use
of the diagnostics parameter is from when the functions themselves
were introduced in 2caf20c52b (test-lib: user-friendly alternatives
to test [-d|-f|-e], 2010-08-10).

But as the the rest of this diff demonstrates its presence did more to
silently introduce bugs in our tests. Fix such bugs in the tests added
in ae4e89e549 (gc: add --keep-largest-pack option, 2018-04-15), and
c04ba51739 (t6046: testcases checking whether updates can be skipped
in a merge, 2018-04-19).

Let's also assert that those functions are called with exactly one
parameter, a follow-up commit will add similar asserts to other
functions in test-lib-functions.sh that we didn't have existing misuse
of.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/README

@@ -917,13 +917,13 @@ library for your script to use.
 
    Check whether a file has the length it is expected to.
 
- - test_path_is_file <path> [<diagnosis>]
-   test_path_is_dir <path> [<diagnosis>]
-   test_path_is_missing <path> [<diagnosis>]
+ - test_path_is_file <path>
+   test_path_is_dir <path>
+   test_path_is_missing <path>
 
    Check if the named path is a file, if the named path is a
    directory, or if the named path does not exist, respectively,
-   and fail otherwise, showing the <diagnosis> text.
+   and fail otherwise.
 
  - test_when_finished <script>
 

t/t3404-rebase-interactive.sh

@@ -101,7 +101,8 @@ test_expect_success 'rebase -i with the exec command' '
 	) &&
 	test_path_is_file touch-one &&
 	test_path_is_file touch-two &&
-	test_path_is_missing touch-three " (should have stopped before)" &&
+	# Missing because we should have stopped by now.
+	test_path_is_missing touch-three &&
 	test_cmp_rev C HEAD &&
 	git rebase --continue &&
 	test_path_is_file touch-three &&

t/t6426-merge-skip-unneeded-updates.sh

@@ -492,7 +492,9 @@ test_expect_success '3a-L: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
 		test_cmp expect actual &&
 
 		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
-		test_path_is_missing bq foo/bq foo/whatever
+		test_path_is_missing bq &&
+		test_path_is_missing foo/bq &&
+		test_path_is_missing foo/whatever
 	)
 '
 
@@ -522,7 +524,9 @@ test_expect_success '3a-R: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
 		test_cmp expect actual &&
 
 		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
-		test_path_is_missing bq foo/bq foo/whatever
+		test_path_is_missing bq &&
+		test_path_is_missing foo/bq &&
+		test_path_is_missing foo/whatever
 	)
 '
 
@@ -588,7 +592,9 @@ test_expect_success '3b-L: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
 		test_cmp expect actual &&
 
 		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
-		test_path_is_missing bq foo/bq foo/whatever
+		test_path_is_missing bq &&
+		test_path_is_missing foo/bq &&
+		test_path_is_missing foo/whatever
 	)
 '
 
@@ -618,7 +624,9 @@ test_expect_success '3b-R: bq_1->foo/bq_2 on A, foo/->bar/ on B' '
 		test_cmp expect actual &&
 
 		test_must_fail git rev-parse HEAD:bq HEAD:foo/bq &&
-		test_path_is_missing bq foo/bq foo/whatever
+		test_path_is_missing bq &&
+		test_path_is_missing foo/bq &&
+		test_path_is_missing foo/whatever
 	)
 '
 

t/t6500-gc.sh

@@ -78,7 +78,7 @@ test_expect_success 'gc --keep-largest-pack' '
 		git gc &&
 		( cd .git/objects/pack && ls *.pack ) >pack-list &&
 		test_line_count = 1 pack-list &&
-		BASE_PACK=.git/objects/pack/pack-*.pack &&
+		cp pack-list base-pack-list &&
 		test_commit four &&
 		git repack -d &&
 		test_commit five &&
@@ -90,7 +90,7 @@ test_expect_success 'gc --keep-largest-pack' '
 		test_line_count = 2 pack-list &&
 		awk "/^P /{print \$2}" <.git/objects/info/packs >pack-info &&
 		test_line_count = 2 pack-info &&
-		test_path_is_file $BASE_PACK &&
+		test_path_is_file .git/objects/pack/$(cat base-pack-list) &&
 		git fsck
 	)
 '

t/test-lib-functions.sh

@@ -717,12 +717,12 @@ test_external_without_stderr () {
 }
 
 # debugging-friendly alternatives to "test [-f|-d|-e]"
-# The commands test the existence or non-existence of $1. $2 can be
-# given to provide a more precise diagnosis.
+# The commands test the existence or non-existence of $1
 test_path_is_file () {
+	test "$#" -ne 1 && BUG "1 param"
 	if ! test -f "$1"
 	then
-		echo "File $1 doesn't exist. $2"
+		echo "File $1 doesn't exist"
 		false
 	fi
 }
@@ -730,15 +730,16 @@ test_path_is_file () {
 test_path_is_dir () {
 	if ! test -d "$1"
 	then
-		echo "Directory $1 doesn't exist. $2"
+		echo "Directory $1 doesn't exist"
 		false
 	fi
 }
 
 test_path_exists () {
+	test "$#" -ne 1 && BUG "1 param"
 	if ! test -e "$1"
 	then
-		echo "Path $1 doesn't exist. $2"
+		echo "Path $1 doesn't exist"
 		false
 	fi
 }