Read command line argument defaults from git config #189

This requires changing command line argument parsing to use a 2-phase process: initially we *only* parse the flags to determine the git config location to use. We then read defaults from this git config for (most of the) remaining arguments added to the 2nd phase parser.

nbstripout/_nbstripout.py

@@ -361,10 +361,47 @@ def _git_config_string(git_config, key):
         return ''
 
 
+def _git_config_flag(git_config, key):
+    key = key if '.' in key else f'filter.nbstripout.{key}'
+    try:
+        return check_output(git_config + ['--type', 'bool', key], universal_newlines=True).strip() == 'true'
+    except (CalledProcessError, FileNotFoundError):
+        return None
+
+
 def main():
-    parser = ArgumentParser(epilog=__doc__, formatter_class=RawDescriptionHelpFormatter)
+    # Don't handle -h/--help with this parser as the argument list is incomplete
+    parser = ArgumentParser(add_help=False)
+
+    location = parser.add_mutually_exclusive_group()
+    location.add_argument('--global', dest='_global', action='store_true',
+                          help='Use global git config (default is local config)')
+    location.add_argument('--system', dest='_system', action='store_true',
+                          help='Use system git config (default is local config)')
+    location.add_argument('--python', dest='_python', metavar="PATH",
+                          help='Path to python executable to use when --install\'ing '
+                          '(default is deduced from `sys.executable`)')
+
+    # Initial parsing of arguments to determine git config location to use.
+    args, _ = parser.parse_known_args()
+    git_config = ['git', 'config']
+
+    if args._system:
+        git_config.append('--system')
+        install_location = INSTALL_LOCATION_SYSTEM
+    elif args._global:
+        git_config.append('--global')
+        install_location = INSTALL_LOCATION_GLOBAL
+    else:
+        git_config.append('--local')
+        install_location = INSTALL_LOCATION_LOCAL
+
+    # 2nd pass parser, using defaults from git config and inheriting from 1st pass
+    parser = ArgumentParser(epilog=__doc__, formatter_class=RawDescriptionHelpFormatter, parents=[parser])
+
     task = parser.add_mutually_exclusive_group()
     task.add_argument('--dry-run', action='store_true',
+                      default=_git_config_flag(git_config, key='dryRun'),
                       help='Print which notebooks would have been stripped')
     task.add_argument('--install', action='store_true',
                       help='Install nbstripout in the current repository (set '
@@ -379,60 +416,53 @@ def main():
                       'repository and configuration summary if installed')
     task.add_argument('--version', action='store_true',
                       help='Print version')
+
     parser.add_argument('--keep-count', action='store_true',
+                        default=_git_config_flag(git_config, key='keepCount'),
                         help='Do not strip the execution count/prompt number')
     parser.add_argument('--keep-output', action='store_true',
-                        help='Do not strip output', default=None)
+                        default=_git_config_flag(git_config, key='keepOutput'),
+                        help='Do not strip output')
     parser.add_argument('--keep-id', action='store_true',
+                        default=_git_config_flag(git_config, key='keepId'),
                         help='Keep the randomly generated cell ids, '
                         'which will be different after each execution.')
-    parser.add_argument('--extra-keys', default='',
+    parser.add_argument('--extra-keys',
+                        default=_git_config_string(git_config, key='extraKeys'),
                         help='Space separated list of extra keys to strip '
-                        'from metadata, e.g. metadata.foo cell.metadata.bar')
-    parser.add_argument('--keep-metadata-keys', default='',
+                        'from metadata, e.g. "metadata.foo cell.metadata.bar"')
+    parser.add_argument('--keep-metadata-keys',
+                        default=_git_config_string(git_config, key='keepMetadataKeys'),
                         help='Space separated list of metadata keys to keep'
-                        ', e.g. metadata.foo cell.metadata.bar')
+                        ', e.g. "metadata.foo cell.metadata.bar"')
     parser.add_argument('--drop-empty-cells', action='store_true',
+                        default=_git_config_flag(git_config, key='dropEmptyCells'),
                         help='Remove cells where `source` is empty or contains only whitepace')
-    parser.add_argument('--drop-tagged-cells', default='',
+    parser.add_argument('--drop-tagged-cells',
+                        default=_git_config_string(git_config, key='dropTaggedCells'),
                         help='Space separated list of cell-tags that remove an entire cell')
     parser.add_argument('--strip-init-cells', action='store_true',
+                        default=_git_config_flag(git_config, key='stripInitCells'),
                         help='Remove cells with `init_cell: true` metadata (default: False)')
     parser.add_argument('--attributes', metavar='FILEPATH',
                         help='Attributes file to add the filter to (in '
                         'combination with --install/--uninstall), '
                         'defaults to .git/info/attributes')
-    location = parser.add_mutually_exclusive_group()
-    location.add_argument('--global', dest='_global', action='store_true',
-                          help='Use global git config (default is local config)')
-    location.add_argument('--system', dest='_system', action='store_true',
-                          help='Use system git config (default is local config)')
-    location.add_argument('--python', dest='_python', metavar="PATH",
-                          help='Path to python executable to use when --install\'ing '
-                          '(default is deduced from `sys.executable`)')
     parser.add_argument('--force', '-f', action='store_true',
+                        default=_git_config_flag(git_config, key='force'),
                         help='Strip output also from files with non ipynb extension')
     parser.add_argument('--max-size', metavar='SIZE',
-                        help='Keep outputs smaller than SIZE', default='0')
-    parser.add_argument('--mode', '-m', default='jupyter', choices=['jupyter', 'zeppelin'],
+                        default=_git_config_string(git_config, key='maxSize') or '0',
+                        help='Keep outputs smaller than SIZE')
+    parser.add_argument('--mode', '-m', choices=['jupyter', 'zeppelin'],
+                        default=_git_config_string(git_config, key='mode') or 'jupyter',
                         help='Specify mode between [jupyter (default) | zeppelin] (to be used in combination with -f)')
 
     parser.add_argument('--textconv', '-t', action='store_true',
                         help='Prints stripped files to STDOUT')
 
     parser.add_argument('files', nargs='*', help='Files to strip output from')
     args = parser.parse_args()
-    git_config = ['git', 'config']
-
-    if args._system:
-        git_config.append('--system')
-        install_location = INSTALL_LOCATION_SYSTEM
-    elif args._global:
-        git_config.append('--global')
-        install_location = INSTALL_LOCATION_GLOBAL
-    else:
-        git_config.append('--local')
-        install_location = INSTALL_LOCATION_LOCAL
 
     if args.install:
         raise SystemExit(install(git_config, install_location, python=args._python, attrfile=args.attributes))
@@ -446,6 +476,7 @@ def main():
         print(__version__)
         raise SystemExit(0)
 
+    # Determine additional metadata keys to strip
     extra_keys = [
         'metadata.signature',
         'metadata.widgets',
@@ -456,12 +487,10 @@ def main():
         'cell.metadata.hidden',
         'cell.metadata.scrolled',
     ]
-
-    extra_keys.extend(_git_config_string(git_config, key='extrakeys').split())
     extra_keys.extend(args.extra_keys.split())
 
-    keep_metadata_keys = _git_config_string(git_config, key='keepmetadatakeys').split()
-    keep_metadata_keys.extend(args.keep_metadata_keys.split())
+    keep_metadata_keys = args.keep_metadata_keys.split()
+
     extra_keys = [i for i in extra_keys if i not in keep_metadata_keys]
 
     # Wrap input/output stream in UTF-8 encoded text wrapper