make flynt incremental (#3905)

Fixes #3901.

check/format-incremental

@@ -35,10 +35,6 @@
 cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 cd "$(git rev-parse --show-toplevel)"
 
-# TODO: Remove '-e cirq/ops/pauli_string.py' once the line is covered (https://github.com/quantumlib/Cirq/issues/3804)
-flynt cirq dev_tools examples -f -e cirq/ops/pauli_string.py
-
-FLYNTSTATUS=$?
 
 # Parse arguments.
 only_print=1
@@ -109,6 +105,16 @@ if (( any_files == 0 )); then
     exit 0
 fi
 
+flynt_args=("--quiet" "-f")
+if (( only_print == 1 )); then
+    flynt_args+=("--dry-run")
+fi
+
+# TODO: Remove '-e cirq/ops/pauli_string.py' once the line is covered (https://github.com/quantumlib/Cirq/issues/3804)
+flynt ${format_files} "${flynt_args[@]}"  -e cirq/ops/pauli_string.py
+FLYNTSTATUS=$?
+
+echo "Running the black formatter..."
 
 args=("--color")
 if (( only_print == 1 )); then

dev_tools/bash_scripts_test.py

@@ -509,12 +509,7 @@ def test_incremental_format_branch_selection(tmpdir_factory):
         script_file='check/format-incremental', tmpdir_factory=tmpdir_factory, arg='HEAD~9999'
     )
     assert result.exit_code == 1
-    assert (
-        result.out
-        == """Running flynt v.0.60
-`cirq` not found
-"""
-    )
+    assert result.out == ''
     assert "No revision 'HEAD~9999'." in result.err
 
     result = run(script_file='check/format-incremental', tmpdir_factory=tmpdir_factory)
@@ -555,12 +550,8 @@ def test_incremental_format_branch_selection(tmpdir_factory):
         setup='git checkout -b other --quiet\ngit branch -D master --quiet\n',
     )
     assert result.exit_code == 1
-    assert (
-        result.out
-        == """Running flynt v.0.60
-`cirq` not found
-"""
-    )
+    assert result.out == ''
+
     assert 'No default revision found to compare against' in result.err
 
     # Works when ambiguous between revision and file.
@@ -598,7 +589,7 @@ def test_incremental_format_branch_selection(tmpdir_factory):
         'git add -A\n'
         'git commit -q -m test3 --no-gpg-sign\n',
     )
-    assert result.exit_code == 1
+    assert result.exit_code == 0
     assert 'INTERCEPTED black --color --check --diff alt.py' in result.out
     assert result.err.startswith("Comparing against revision 'master' (merge base ")