[GSOC][PATCH v3] t3701: don't lose "git" exit codes in test scripts

[Edwin Fernando <edwinfernando734@gmail.com>]

Exit codes are lost due to piping and command substitution:

- "git ... | <command>"
- "<command> $(git ... )"

Fix these issues using the intermediate step of writing output to file.

Signed-off-by: Edwin Fernando <edwinfernando734@gmail.com>
---
Changes from v2:
- use git rebase to squash commit history,
  and diff with upstream commit for review
- use present tense for code before the commit.

 t/t3701-add-interactive.sh | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 3a99837d9b..77aad9032a 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -292,8 +292,10 @@ test_expect_success FILEMODE 'patch does not affect mode' '
 	echo content >>file &&
 	chmod +x file &&
 	printf "n\\ny\\n" | git add -p &&
-	git show :file | grep content &&
-	git diff file | grep "new mode"
+	git show :file >show &&
+	grep content show &&
+	git diff file >diff &&
+	grep "new mode" diff
 '
 
 test_expect_success FILEMODE 'stage mode but not hunk' '
@@ -301,8 +303,10 @@ test_expect_success FILEMODE 'stage mode but not hunk' '
 	echo content >>file &&
 	chmod +x file &&
 	printf "y\\nn\\n" | git add -p &&
-	git diff --cached file | grep "new mode" &&
-	git diff          file | grep "+content"
+	git diff --cached file >diff &&
+	grep "new mode" diff &&
+	git diff file >diff &&
+	grep "+content" diff
 '
 
 
@@ -311,9 +315,11 @@ test_expect_success FILEMODE 'stage mode and hunk' '
 	echo content >>file &&
 	chmod +x file &&
 	printf "y\\ny\\n" | git add -p &&
-	git diff --cached file | grep "new mode" &&
-	git diff --cached file | grep "+content" &&
-	test -z "$(git diff file)"
+	git diff --cached file >diff &&
+	grep "new mode" diff &&
+	grep "+content" diff &&
+	git diff file >diff &&
+	test_must_be_empty diff
 '
 
 # end of tests disabled when filemode is not usable
-- 
2.40.0