Replace --rootdir (-r) with --source-dir (-S)

Experience with real codebases suggests that we will eventually want to support
the ability to independently identify source and build directories.

This commit does not add that functionality, but introduces the "source
directory" as a replacement for the concept of a "root directory" without
breaking backwards compatibility.

Signed-off-by: John Pennycook <[email protected]>

codebasin.py

@@ -9,6 +9,7 @@
 import logging
 import os
 import sys
+import warnings
 
 from codebasin import config, finder, report, util
 from codebasin.walkers.platform_mapper import PlatformMapper
@@ -47,10 +48,18 @@ def main():
         "--rootdir",
         dest="rootdir",
         metavar="DIR",
-        default=os.getcwd(),
-        type=str,
+        default=None,
         help="Set working root directory (default .)",
     )
+    parser.add_argument(
+        "-S",
+        "--source-dir",
+        metavar="<path>",
+        dest="source_dir",
+        default=None,
+        help="Set path to source directory. "
+        + "The default is the current directory.",
+    )
     parser.add_argument(
         "-c",
         "--config",
@@ -131,7 +140,23 @@ def main():
     logging.getLogger("codebasin").setLevel(
         max(1, logging.WARNING - 10 * (args.verbose - args.quiet)),
     )
-    rootdir = os.path.realpath(args.rootdir)
+
+    # Determine the root directory based on the -S and -r flags.
+    rootpath = None
+    if args.source_dir and args.rootdir:
+        raise RuntimeError(
+            "Cannot specify both --source-dir (-S) and --rootdir (-r).",
+        )
+    if not args.source_dir and not args.rootdir:
+        rootpath = os.getcwd()
+    elif args.source_dir:
+        rootpath = args.source_dir
+    elif args.rootdir:
+        warnings.warn(
+            "--rootdir (-r) is deprecated. Use --source-dir (-S) instead.",
+        )
+        rootpath = args.rootdir
+    rootdir = os.path.realpath(rootpath)
 
     # Process the -p flag first to infer wider context.
     filtered_platforms = []