utils: Log subprocess calls

Makes 'git pw --debug ...' a little more useful.

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

git_pw/utils.py

@@ -4,6 +4,7 @@
 
 import csv
 import io
+import logging
 import os
 import subprocess
 import sys
@@ -12,6 +13,8 @@
 import click
 from tabulate import tabulate
 
+LOG = logging.getLogger(__name__)
+
 
 def ensure_str(s: ty.Any) -> str:
     if s is None:
@@ -35,8 +38,13 @@ def git_config(value: str) -> str:
     Returns:
         Matching setting for ``key`` if available, else None.
     """
+    cmd = ['git', 'config', value]
+
+    LOG.debug('Fetching git config info for %s', value)
+    LOG.debug('Running: %s', ' '.join(cmd))
+
     try:
-        output = subprocess.check_output(['git', 'config', value])
+        output = subprocess.check_output(cmd)
     except subprocess.CalledProcessError:
         output = b''
 
@@ -52,6 +60,9 @@ def git_am(mbox: str, args: ty.Tuple[str, ...]) -> None:
         cmd.append('-3')
     cmd.append(mbox)
 
+    LOG.debug('Applying patch at %s', mbox)
+    LOG.debug('Running: %s', ' '.join(cmd))
+
     try:
         output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError as exc: