presubmit: Don't use chromite in presubmit hook

We can do the things chromite.lib was doing in other ways while making
it easier to run the presubmit hooks outside of the chroot. Replace the
command line parsing with `argparse` and use `subprocess` for
interfacting with Git.

BUG=None
TEST=./util/check_low_coverage_reason.py

Change-Id: I6ecc692ae26d1646604f2cabd52c76337404a481
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4545398
Commit-Queue: Jeremy Bettis <jbettis@chromium.org>
Tested-by: Tristan Honscheid <honscheid@google.com>
Auto-Submit: Tristan Honscheid <honscheid@google.com>
Reviewed-by: Jeremy Bettis <jbettis@chromium.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/util/check_low_coverage_reason.py b/util/check_low_coverage_reason.py
index c6119f6a6a..52138dc180 100755
--- a/util/check_low_coverage_reason.py
+++ b/util/check_low_coverage_reason.py
@@ -5,15 +5,13 @@
 
 """Ensure commit messages using LOW_COVERAGE_REASON include a bug."""
 
+import argparse
 import logging
 import pathlib
 import re
+import subprocess
 import sys
 
-from chromite.lib import commandline
-from chromite.lib import cros_build_lib
-from chromite.lib import git
-
 
 # Look for LOW_COVERAGE_REASON and then an optional b{:|/}number bug reference.
 LOW_COV_REGEX = re.compile(
@@ -24,7 +22,7 @@ EC_BASE = pathlib.Path(__file__).resolve().parent.parent
 
 def main(argv=None):
     """Check for bug in LOW_COVERAGE_REASON."""
-    parser = commandline.ArgumentParser()
+    parser = argparse.ArgumentParser()
     parser.add_argument(
         "commit_id",
         help="Commit whose message will be checked.",
@@ -36,13 +34,16 @@ def main(argv=None):
         return 0
 
     try:
-        commit_log = git.Log(EC_BASE, rev=opts.commit_id, max_count=1)
-    except cros_build_lib.RunCommandError as err:
-        logging.error("Unable to query git log: %s", str(err))
+        commit_log = subprocess.check_output(
+            ["git", "log", "--max-count=1", opts.commit_id],
+            cwd=EC_BASE,
+        )
+    except subprocess.CalledProcessError as err:
+        logging.error("Unable to query git log: %s", err)
         return 1
 
     # Search commit message for LOW_COVERAGE_REASON and bug
-    matches = LOW_COV_REGEX.findall(commit_log)
+    matches = LOW_COV_REGEX.findall(commit_log.decode())
     if matches and not any({m[2] for m in matches}):
         # We have LOW_COVERAGE_REASON line(s) but none include a bug
         logging.error(