[PATCH 1/4] test-lib-functions: introduce test_line_count_cmd

[Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx>]

In Git project, we have multiple occasions that requires checking number
of lines of text in stdout and/or stderr of a command. One of such
example is t6400, which checks number of files in various states.

Some of those commands are Git command, and we would like to check their
exit status.  In some of those checks, we pipe the stdout of those
commands to "wc -l" to check for line count, thus loosing the exit status.

Introduce a helper function to check for number of lines in stdout and
stderr from those commands.

This helper will create 2 temporary files in process, thus it may affect
output of some checks.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx>
---

Notes:
    Theoretically, we could avoid those temporary files by this shenanigan:
    
    	! (
    	  test $(
    		(
    		  test $(
    			  ( "$@" || echo "'$*' run into failure" >&3) | wc -l
    			)
    			"$out_ops" "$out_val" ||
    		  echo "stdout: !$outop $outval '$*'" >&3
    		) 2>&1 | wc -l
    	  ) "$errop" "$errval" ||
    	  echo "stderr: !$errop $errval '$*'" >&3
    	) 3>&1 | grep .
    
    However, it looks too complicated.

 t/test-lib-functions.sh | 64 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index b823c14027..85bb31ea4c 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -817,6 +817,70 @@ test_line_count () {
 	fi
 }
 
+# test_line_count_cmd checks the number of lines of captured stdout and/or
+# stderr of a command.
+#
+# NOTE: this helper function will create 2 temporary files named:
+# * test_line_count_cmd_.out; and
+# * test_line_count_cmd_.err
+#
+# And this helper function will remove those 2 files if the check is succeed.
+# In case of failure, those files will be preserved.
+test_line_count_cmd () {
+	local outop outval
+	local errop errval
+
+	while test $# -ge 3
+	do
+		case "$1" in
+		--out)
+			outop="$2"
+			outval="$3"
+			;;
+		--err)
+			errop="$2"
+			errval="$3"
+			;;
+		*)
+			break
+			;;
+		esac
+		shift 3
+	done &&
+	if test $# = 0 ||
+	   { test "x$1" = "x!" && test $# = 1 ; }
+	then
+		BUG "test_line_count_cmd: no command to be run"
+	fi &&
+	if test -z "$outop$errop"
+	then
+		BUG "test_line_count_cmd: check which stream?"
+	fi &&
+
+	if test "x$1" = "x!" 
+	then
+		shift &&
+		if "$@" >test_line_count_cmd_.out 2>test_line_count_cmd_.err
+		then
+			echo "error: '$@' succeed!"
+			return 1
+		fi
+	elif ! "$@" >test_line_count_cmd_.out 2>test_line_count_cmd_.err
+	then
+		echo "error: '$@' run into failure!"
+		return 1
+	fi &&
+	if test -n "$outop"
+	then
+		test_line_count "$outop" "$outval" test_line_count_cmd_.out
+	fi &&
+	if test -n "$errop"
+	then
+		test_line_count "$errop" "$errval" test_line_count_cmd_.err
+	fi &&
+	rm -f test_line_count_cmd_.out test_line_count_cmd_.err
+}
+
 test_file_size () {
 	test "$#" -ne 1 && BUG "1 param"
 	test-tool path-utils file-size "$1"
-- 
2.32.0.278.gd42b80f139