Merge branch 'ps/difftool-dir-diff-exit-code' into HEAD

"git difftool --dir-diff" learned to honor the "--trust-exit-code"
option; it used to always exit with 0 and signalled success.

* ps/difftool-dir-diff-exit-code:
  git-difftool--helper: honor `--trust-exit-code` with `--dir-diff`

Documentation/git-difftool.txt

@@ -105,7 +105,6 @@ instead.  `--no-symlinks` is the default on Windows.
 	`merge.tool` until a tool is found.
 
 --[no-]trust-exit-code::
-	'git-difftool' invokes a diff tool individually on each file.
 	Errors reported by the diff tool are ignored by default.
 	Use `--trust-exit-code` to make 'git-difftool' exit when an
 	invoked diff tool returns a non-zero exit code.

git-difftool--helper.sh

@@ -91,6 +91,19 @@ then
 	# ignore the error from the above --- run_merge_tool
 	# will diagnose unusable tool by itself
 	run_merge_tool "$merge_tool" false
+
+	status=$?
+	if test $status -ge 126
+	then
+		# Command not found (127), not executable (126) or
+		# exited via a signal (>= 128).
+		exit $status
+	fi
+
+	if test "$GIT_DIFFTOOL_TRUST_EXIT_CODE" = true
+	then
+		exit $status
+	fi
 else
 	# Launch the merge tool on each path provided by 'git diff'
 	while test $# -gt 6

t/t7800-difftool.sh

@@ -91,58 +91,67 @@ test_expect_success 'difftool forwards arguments to diff' '
 	rm for-diff
 '
 
-test_expect_success 'difftool ignores exit code' '
-	test_config difftool.error.cmd false &&
-	git difftool -y -t error branch
-'
+for opt in '' '--dir-diff'
+do
+	test_expect_success "difftool ${opt} ignores exit code" "
+		test_config difftool.error.cmd false &&
+		git difftool ${opt} -y -t error branch
+	"
 
-test_expect_success 'difftool forwards exit code with --trust-exit-code' '
-	test_config difftool.error.cmd false &&
-	test_must_fail git difftool -y --trust-exit-code -t error branch
-'
+	test_expect_success "difftool ${opt} forwards exit code with --trust-exit-code" "
+		test_config difftool.error.cmd false &&
+		test_must_fail git difftool ${opt} -y --trust-exit-code -t error branch
+	"
 
-test_expect_success 'difftool forwards exit code with --trust-exit-code for built-ins' '
-	test_config difftool.vimdiff.path false &&
-	test_must_fail git difftool -y --trust-exit-code -t vimdiff branch
-'
+	test_expect_success "difftool ${opt} forwards exit code with --trust-exit-code for built-ins" "
+		test_config difftool.vimdiff.path false &&
+		test_must_fail git difftool ${opt} -y --trust-exit-code -t vimdiff branch
+	"
 
-test_expect_success 'difftool honors difftool.trustExitCode = true' '
-	test_config difftool.error.cmd false &&
-	test_config difftool.trustExitCode true &&
-	test_must_fail git difftool -y -t error branch
-'
+	test_expect_success "difftool ${opt} honors difftool.trustExitCode = true" "
+		test_config difftool.error.cmd false &&
+		test_config difftool.trustExitCode true &&
+		test_must_fail git difftool ${opt} -y -t error branch
+	"
 
-test_expect_success 'difftool honors difftool.trustExitCode = false' '
-	test_config difftool.error.cmd false &&
-	test_config difftool.trustExitCode false &&
-	git difftool -y -t error branch
-'
+	test_expect_success "difftool ${opt} honors difftool.trustExitCode = false" "
+		test_config difftool.error.cmd false &&
+		test_config difftool.trustExitCode false &&
+		git difftool ${opt} -y -t error branch
+	"
 
-test_expect_success 'difftool ignores exit code with --no-trust-exit-code' '
-	test_config difftool.error.cmd false &&
-	test_config difftool.trustExitCode true &&
-	git difftool -y --no-trust-exit-code -t error branch
-'
+	test_expect_success "difftool ${opt} ignores exit code with --no-trust-exit-code" "
+		test_config difftool.error.cmd false &&
+		test_config difftool.trustExitCode true &&
+		git difftool ${opt} -y --no-trust-exit-code -t error branch
+	"
 
-test_expect_success 'difftool stops on error with --trust-exit-code' '
-	test_when_finished "rm -f for-diff .git/fail-right-file" &&
-	test_when_finished "git reset -- for-diff" &&
-	write_script .git/fail-right-file <<-\EOF &&
-	echo failed
-	exit 1
-	EOF
-	>for-diff &&
-	git add for-diff &&
-	test_must_fail git difftool -y --trust-exit-code \
-		--extcmd .git/fail-right-file branch >actual &&
-	test_line_count = 1 actual
-'
+	test_expect_success "difftool ${opt} stops on error with --trust-exit-code" "
+		test_when_finished 'rm -f for-diff .git/fail-right-file' &&
+		test_when_finished 'git reset -- for-diff' &&
+		write_script .git/fail-right-file <<-\EOF &&
+		echo failed
+		exit 1
+		EOF
+		>for-diff &&
+		git add for-diff &&
+		test_must_fail git difftool ${opt} -y --trust-exit-code \
+			--extcmd .git/fail-right-file branch >actual &&
+		test_line_count = 1 actual
+	"
 
-test_expect_success 'difftool honors exit status if command not found' '
-	test_config difftool.nonexistent.cmd i-dont-exist &&
-	test_config difftool.trustExitCode false &&
-	test_must_fail git difftool -y -t nonexistent branch
-'
+	test_expect_success "difftool ${opt} honors exit status if command not found" "
+		test_config difftool.nonexistent.cmd i-dont-exist &&
+		test_config difftool.trustExitCode false &&
+		if test "${opt}" = '--dir-diff'
+		then
+			expected_code=127
+		else
+			expected_code=128
+		fi &&
+		test_expect_code \${expected_code} git difftool ${opt} -y -t nonexistent branch
+	"
+done
 
 test_expect_success 'difftool honors --gui' '
 	difftool_test_setup &&