Make `targetDir` absolute by default

When serving a `../` as directory (with `-l`), servefile creates an
endless 301-redirect loop. Having an absolute path fixes this. Since
this error might come up any time again, we're setting `targetDir` to
its absolute path right from the beginning and never have to worry about
it later on.

servefile

@@ -312,7 +312,7 @@ class DirListingHandler(FileBaseHandler):
 		path = self.getCleanPath()
 
 		# check if path is in current serving directory
-		currBaseDir = os.path.abspath(self.targetDir) + os.path.sep
+		currBaseDir = self.targetDir + os.path.sep
 		requestPath = os.path.normpath(os.path.join(currBaseDir, path)) + os.path.sep
 		if not requestPath.startswith(currBaseDir):
 			self.send_response(301)
@@ -1041,7 +1041,7 @@ class ServeFile():
 					raise ServeFileException("Error: Could not create directory '%s' for uploads, %r" % (self.target, str(e)))
 			else:
 				raise ServeFileException("Error: Upload directory already exists and is a file.")
-			FilePutter.targetDir = self.target
+			FilePutter.targetDir = os.path.abspath(self.target)
 			FilePutter.maxUploadSize = self.maxUploadSize
 			handler = FilePutter
 		elif self.serveMode == self.MODE_LISTDIR:
@@ -1050,7 +1050,7 @@ class ServeFile():
 			if not os.path.isdir(self.target):
 				raise ServeFileException("Error: '%s' is not a directory." % (self.target,))
 			handler = DirListingHandler
-			handler.targetDir = self.target
+			handler.targetDir = os.path.abspath(self.target)
 
 		if self.auth:
 			# do authentication

tests/test_servefile.py

@@ -167,6 +167,33 @@ def test_serve_directory(run_servefile, datadir):
     check_download('jup!', '/bar/thisisaverylongfilenamefortestingthatthisstillworksproperly')
 
 
+def test_serve_relative_directory(run_servefile, datadir):
+    d = {
+        'foo': {'kratzbaum': 'cat', 'I like Cats!': 'kitteh', '&&&&&&&': 'wheee'},
+        'bar': {'thisisaverylongfilenamefortestingthatthisstillworksproperly': 'jup!'},
+        'noot': 'still data in here',
+        'bigfile': 'x' * (10 * 1024 ** 2),
+    }
+    p = datadir(d)
+    run_servefile(['../', '-l'], cwd=os.path.join(str(p), 'foo'))
+
+    # check if all files are in directory listing
+    # (could be made more sophisticated with beautifulsoup)
+    for path in '/', '/../':
+        r = make_request(path)
+        for k in d:
+            assert k in r.text
+
+    for fname, content in d['foo'].items():
+        check_download(content, '/foo/' + fname)
+
+    r = make_request('/unknown')
+    assert r.status_code == 404
+
+    # download
+    check_download('jup!', '/bar/thisisaverylongfilenamefortestingthatthisstillworksproperly')
+
+
 def test_upload(run_servefile, tmp_path):
     data = ('this is my live now\n'
             'uploading strings to servers\n'