Add comprehensive tests for --quiet flag

9 tests covering:
- Silent output on successful build
- Normal mode still shows output (control test)
- Errors still printed in quiet mode
- Quiet propagates to nested child builds
- --quiet long form
- -q combined with -k flag
- Multiple targets with -q
- Build correctness unaffected by -q
- Nested build errors show error chain in quiet mode

Author: dinkelk

test/150-quiet/all.do

@@ -0,0 +1,116 @@
+exec >&2
+. ../skip-if-minimal-do.sh
+
+# Test 1: With -q, successful build produces no output
+echo "Test 1: quiet mode suppresses output on success"
+rm -f target1
+output=$(redo -q target1 2>&1)
+if [ -n "$output" ]; then
+    echo "FAIL: expected no output with -q, got: $output" >&2
+    exit 1
+fi
+[ -e target1 ] || exit 2
+echo "  PASS"
+
+# Test 2: Without -q, successful build produces output
+echo "Test 2: normal mode shows output"
+rm -f target1
+output=$(redo target1 2>&1)
+if [ -z "$output" ]; then
+    echo "FAIL: expected output without -q" >&2
+    exit 3
+fi
+echo "  PASS"
+
+# Test 3: With -q, errors are still printed
+echo "Test 3: quiet mode still shows errors"
+rm -f failme
+set +e
+output=$(redo -q failme 2>&1)
+rc=$?
+set -e
+if [ "$rc" -eq 0 ]; then
+    echo "FAIL: expected non-zero exit" >&2
+    exit 4
+fi
+if [ -z "$output" ]; then
+    echo "FAIL: expected error output with -q on failure" >&2
+    exit 5
+fi
+case "$output" in
+    *Error*) ;; # good
+    *) echo "FAIL: expected 'Error' in output, got: $output" >&2; exit 6 ;;
+esac
+echo "  PASS"
+
+# Test 4: -q propagates to child redo processes (nested builds)
+echo "Test 4: quiet mode propagates to nested builds"
+rm -f outer inner
+output=$(redo -q outer 2>&1)
+if [ -n "$output" ]; then
+    echo "FAIL: expected no output from nested -q build, got: $output" >&2
+    exit 7
+fi
+[ -e outer ] || exit 8
+[ -e inner ] || exit 9
+echo "  PASS"
+
+# Test 5: --quiet long form works
+echo "Test 5: --quiet long form"
+rm -f target1
+output=$(redo --quiet target1 2>&1)
+if [ -n "$output" ]; then
+    echo "FAIL: expected no output with --quiet, got: $output" >&2
+    exit 10
+fi
+echo "  PASS"
+
+# Test 6: -q combined with other flags
+echo "Test 6: -q combined with -k (keep-going)"
+rm -f target1
+output=$(redo -q -k target1 2>&1)
+if [ -n "$output" ]; then
+    echo "FAIL: expected no output with -q -k, got: $output" >&2
+    exit 11
+fi
+echo "  PASS"
+
+# Test 7: -q with multiple targets
+echo "Test 7: -q with multiple targets"
+rm -f target1 inner
+output=$(redo -q target1 inner 2>&1)
+if [ -n "$output" ]; then
+    echo "FAIL: expected no output with -q and multiple targets, got: $output" >&2
+    exit 12
+fi
+[ -e target1 ] || exit 13
+[ -e inner ] || exit 14
+echo "  PASS"
+
+# Test 8: -q doesn't affect build correctness (target content is right)
+echo "Test 8: -q doesn't affect build output content"
+rm -f target1
+redo -q target1
+content=$(cat target1)
+if [ "$content" != "built" ]; then
+    echo "FAIL: expected 'built' in target1, got: $content" >&2
+    exit 15
+fi
+echo "  PASS"
+
+# Test 9: Nested error in quiet mode still shows error chain
+echo "Test 9: nested error in quiet mode shows error chain"
+rm -f outer_fail inner_fail
+set +e
+output=$(redo -q outer_fail 2>&1)
+rc=$?
+set -e
+if [ "$rc" -eq 0 ]; then
+    echo "FAIL: expected non-zero exit from outer_fail" >&2
+    exit 16
+fi
+case "$output" in
+    *Error*) ;; # good
+    *) echo "FAIL: expected error output, got: $output" >&2; exit 17 ;;
+esac
+echo "  PASS"

test/150-quiet/failme.do

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+exit 1

test/150-quiet/inner.do

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+echo "inner" > "$3"

test/150-quiet/inner_fail.do

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+exit 1

test/150-quiet/outer.do

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+redo-ifchange inner
+echo "outer" > "$3"

test/150-quiet/outer_fail.do

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+redo-ifchange inner_fail
+echo "should not reach here" > "$3"

test/150-quiet/target1.do

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+echo "built" > "$3"