[PATCH v3 2/2] tests(mingw): avoid very slow `mingw_test_cmp`

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

It is more performant to run `git diff --no-index` than running the
`mingw_test_cmp` code with MSYS2's Bash, i.e. the Bash that Git for
Windows uses. And a lot more readable.

Note: Earlier attempts at fixing this involved a test helper that avoids
the overhead of the diff machinery, in favor of implementing a behavior
that is more in line with what `mingw_test_cmp` does now, but that
attempt saw a lot of backlash and distractions during review and was
therefore abandoned.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/test-lib-functions.sh | 66 -----------------------------------------
 t/test-lib.sh           |  2 +-
 2 files changed, 1 insertion(+), 67 deletions(-)

diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 8c44856eaec..452fe9bc8aa 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1541,72 +1541,6 @@ test_skip_or_die () {
 	error "$2"
 }
 
-# The following mingw_* functions obey POSIX shell syntax, but are actually
-# bash scripts, and are meant to be used only with bash on Windows.
-
-# A test_cmp function that treats LF and CRLF equal and avoids to fork
-# diff when possible.
-mingw_test_cmp () {
-	# Read text into shell variables and compare them. If the results
-	# are different, use regular diff to report the difference.
-	local test_cmp_a= test_cmp_b=
-
-	# When text came from stdin (one argument is '-') we must feed it
-	# to diff.
-	local stdin_for_diff=
-
-	# Since it is difficult to detect the difference between an
-	# empty input file and a failure to read the files, we go straight
-	# to diff if one of the inputs is empty.
-	if test -s "$1" && test -s "$2"
-	then
-		# regular case: both files non-empty
-		mingw_read_file_strip_cr_ test_cmp_a <"$1"
-		mingw_read_file_strip_cr_ test_cmp_b <"$2"
-	elif test -s "$1" && test "$2" = -
-	then
-		# read 2nd file from stdin
-		mingw_read_file_strip_cr_ test_cmp_a <"$1"
-		mingw_read_file_strip_cr_ test_cmp_b
-		stdin_for_diff='<<<"$test_cmp_b"'
-	elif test "$1" = - && test -s "$2"
-	then
-		# read 1st file from stdin
-		mingw_read_file_strip_cr_ test_cmp_a
-		mingw_read_file_strip_cr_ test_cmp_b <"$2"
-		stdin_for_diff='<<<"$test_cmp_a"'
-	fi
-	test -n "$test_cmp_a" &&
-	test -n "$test_cmp_b" &&
-	test "$test_cmp_a" = "$test_cmp_b" ||
-	eval "diff -u \"\$@\" $stdin_for_diff"
-}
-
-# $1 is the name of the shell variable to fill in
-mingw_read_file_strip_cr_ () {
-	# Read line-wise using LF as the line separator
-	# and use IFS to strip CR.
-	local line
-	while :
-	do
-		if IFS=$'\r' read -r -d $'\n' line
-		then
-			# good
-			line=$line$'\n'
-		else
-			# we get here at EOF, but also if the last line
-			# was not terminated by LF; in the latter case,
-			# some text was read
-			if test -z "$line"
-			then
-				# EOF, really
-				break
-			fi
-		fi
-		eval "$1=\$$1\$line"
-	done
-}
-
 # Like "env FOO=BAR some-program", but run inside a subshell, which means
 # it also works for shell functions (though those functions cannot impact
 # the environment outside of the test_env invocation).
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 7726d1da88a..f8c6205e08f 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1546,7 +1546,7 @@ case $uname_s in
 	test_set_prereq SED_STRIPS_CR
 	test_set_prereq GREP_STRIPS_CR
 	test_set_prereq WINDOWS
-	GIT_TEST_CMP=mingw_test_cmp
+	GIT_TEST_CMP="GIT_DIR=/dev/null git diff --no-index --ignore-cr-at-eol --"
 	;;
 *CYGWIN*)
 	test_set_prereq POSIXPERM
-- 
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