[PATCH] test_cmp: diagnose incorrect arguments more precisely

[Eric Sunshine <sunshine@sunshineco.com>]

d572f52a64 (test_cmp: diagnose incorrect arguments, 2020-08-09) taught
test_cmp() and test_cmp_bin() to diagnose a missing input source. Even
though the arguments to test_cmp() must name regular files (or standard
input), it only diagnoses whether a source is missing, which makes the
check a bit loose. Teach the check to be more precise by diagnosing, not
only a missing source, but also if the source is not a regular file.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---

  On Wed, Sep 16, 2020 at 5:14 PM Junio C Hamano <gitster@pobox.com> wrote:
  > Eric Sunshine <sunshine@sunshineco.com> writes:
  > > [...] I ask because test_cmp() was updated not long ago to
  > > provide better diagnostics when one of the files is missing.
  > > [1]: d572f52a64 (test_cmp: diagnose incorrect arguments, 2020-08-09)
  >
  > Yes, you did this with the commit,
  >         test "x$1" = x- || test -e "$1" || BUG "test_cmp '$1' missing"
  >         test "x$2" = x- || test -e "$2" || BUG "test_cmp '$2' missing"
  > and I do not immediately see why "test -e" shouldn't be "test -f".
  > It should ideally be "stdin is OK, otherwise it must be a readable
  > regular file".

  Perhaps the present patch suitably address your concern?

 t/test-lib-functions.sh | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 8d59b90348..4bc54e9e80 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -955,8 +955,8 @@ test_cmp() {
 	test $# -eq 2 || BUG "test_cmp requires two arguments"
 	if ! eval "$GIT_TEST_CMP" '"$@"'
 	then
-		test "x$1" = x- || test -e "$1" || BUG "test_cmp '$1' missing"
-		test "x$2" = x- || test -e "$2" || BUG "test_cmp '$2' missing"
+		test "x$1" = x- || test -f "$1" || BUG "test_cmp '$1' missing or not regular file"
+		test "x$2" = x- || test -f "$2" || BUG "test_cmp '$2' missing or not regular file"
 		return 1
 	fi
 }
@@ -990,8 +990,8 @@ test_cmp_bin() {
 	test $# -eq 2 || BUG "test_cmp_bin requires two arguments"
 	if ! cmp "$@"
 	then
-		test "x$1" = x- || test -e "$1" || BUG "test_cmp_bin '$1' missing"
-		test "x$2" = x- || test -e "$2" || BUG "test_cmp_bin '$2' missing"
+		test "x$1" = x- || test -f "$1" || BUG "test_cmp_bin '$1' missing or not regular file"
+		test "x$2" = x- || test -f "$2" || BUG "test_cmp_bin '$2' missing or not regular file"
 		return 1
 	fi
 }
-- 
2.28.0.942.g77c4c6094c