commit: pass ChangingFiles object as argument to _process_files

Instead of returning it, we pass it as an argument. This makes the whole if-else
in `_prepare_files` a bit simpler. Else each if-else branch was creating the
object.
13 jobs for topic/default/merge-newnode-final in 41 minutes and 12 seconds (queued for 2 minutes and 11 seconds)
Status Job ID Name Coverage
  Test
passed checks-py2 #111322

00:06:27

passed checks-py3 #111323

00:03:11

passed rust-cargo-test-py2 #111324

00:02:02

passed rust-cargo-test-py3 #111325

00:02:09

passed rust-cargo-test-py3-dirstate-tree #111326

00:01:45

passed test-py2 #111327

00:28:16

failed test-py2-chg #111334

00:21:55

passed test-py2-pure #111329

00:15:46

passed test-py2-rust #111331

00:28:56

passed test-py3 #111328

00:19:04

passed test-py3-pure #111330

00:17:50

passed test-py3-rust #111332

00:16:57

passed test-py3-rust-dirstate-tree #111333

00:18:14

 
Name Stage Failure
failed
test-py2-chg Test
Skipped test-verify-repo-operations.py: missing feature: allow slow tests (use --allow-slow-tests)
Skipped test-wireproto-command-capabilities.t: system supports running with chg
Skipped test-wireproto-exchangev2-shallow.t: missing feature: sqlite3 module is available
Failed test-narrow-exchange.t#lfs-on: output changed
# Ran 850 tests, 91 skipped, 1 failed.
python hash seed: 1204096840
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1