diff --git a/tools/server_lib/lister.py b/tools/server_lib/lister.py
new file mode 100755
index 0000000..3f3b0a6
--- /dev/null
+++ b/tools/server_lib/lister.py
@@ -0,0 +1,131 @@
+#!/usr/bin/env python
+from __future__ import print_function
+from __future__ import absolute_import
+
+import os
+from os.path import abspath
+import sys
+import subprocess
+import re
+from collections import defaultdict
+import argparse
+from six.moves import filter
+
+from typing import Union, List, Dict
+
+def get_ftype(fpath, use_shebang):
+    # type: (str, bool) -> str
+    ext = os.path.splitext(fpath)[1]
+    if ext:
+        return ext[1:]
+    elif use_shebang:
+        # opening a file may throw an OSError
+        with open(fpath) as f:
+            first_line = f.readline()
+            if re.search(r'^#!.*\bpython', first_line):
+                return 'py'
+            elif re.search(r'^#!.*sh', first_line):
+                return 'sh'
+            elif re.search(r'^#!.*\bperl', first_line):
+                return 'pl'
+            elif re.search(r'^#!.*\bnode', first_line):
+                return 'js'
+            elif re.search(r'^#!.*\bruby', first_line):
+                return 'rb'
+            elif re.search(r'^#!', first_line):
+                print('Error: Unknown shebang in file "%s":\n%s' % (fpath, first_line), file=sys.stderr)
+                return ''
+            else:
+                return ''
+    else:
+        return ''
+
+def list_files(targets=[], ftypes=[], use_shebang=True, modified_only=False,
+               exclude=[], group_by_ftype=False, extless_only=False):
+    # type: (List[str], List[str], bool, bool, List[str], bool, bool) -> Union[Dict[str, List[str]], List[str]]
+    """
+    List files tracked by git.
+
+    Returns a list of files which are either in targets or in directories in targets.
+    If targets is [], list of all tracked files in current directory is returned.
+
+    Other arguments:
+    ftypes - List of file types on which to filter the search.
+        If ftypes is [], all files are included.
+    use_shebang - Determine file type of extensionless files from their shebang.
+    modified_only - Only include files which have been modified.
+    exclude - List of paths to be excluded, relative to repository root.
+    group_by_ftype - If True, returns a dict of lists keyed by file type.
+        If False, returns a flat list of files.
+    extless_only - Only include extensionless files in output.
+    """
+    ftypes = [x.strip('.') for x in ftypes]
+    ftypes_set = set(ftypes)
+
+    # Really this is all bytes -- it's a file path -- but we get paths in
+    # sys.argv as str, so that battle is already lost.  Settle for hoping
+    # everything is UTF-8.
+    repository_root = subprocess.check_output(['git', 'rev-parse', '--show-toplevel']).strip().decode('utf-8')
+    exclude_abspaths = [os.path.join(repository_root, fpath).rstrip('/') for fpath in exclude]
+
+    cmdline = ['git', 'ls-files'] + targets
+    if modified_only:
+        cmdline.append('-m')
+
+    files_gen = (x.strip() for x in subprocess.check_output(cmdline, universal_newlines=True).split('\n'))
+    # throw away empty lines and non-files (like symlinks)
+    files = list(filter(os.path.isfile, files_gen))
+
+    result_dict = defaultdict(list)  # type: Dict[str, List[str]]
+    result_list = []  # type: List[str]
+
+    for fpath in files:
+        # this will take a long time if exclude is very large
+        ext = os.path.splitext(fpath)[1]
+        if extless_only and ext:
+            continue
+        absfpath = abspath(fpath)
+        if any(absfpath == expath or absfpath.startswith(expath + '/')
+               for expath in exclude_abspaths):
+            continue
+
+        if ftypes or group_by_ftype:
+            try:
+                filetype = get_ftype(fpath, use_shebang)
+            except (OSError, UnicodeDecodeError) as e:
+                etype = e.__class__.__name__
+                print('Error: %s while determining type of file "%s":' % (etype, fpath), file=sys.stderr)
+                print(e, file=sys.stderr)
+                filetype = ''
+            if ftypes and filetype not in ftypes_set:
+                continue
+
+        if group_by_ftype:
+            result_dict[filetype].append(fpath)
+        else:
+            result_list.append(fpath)
+
+    if group_by_ftype:
+        return result_dict
+    else:
+        return result_list
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="List files tracked by git and optionally filter by type")
+    parser.add_argument('targets', nargs='*', default=[],
+                        help='''files and directories to include in the result.
+                        If this is not specified, the current directory is used''')
+    parser.add_argument('-m', '--modified', action='store_true', default=False, help='list only modified files')
+    parser.add_argument('-f', '--ftypes', nargs='+', default=[],
+                        help="list of file types to filter on. All files are included if this option is absent")
+    parser.add_argument('--ext-only', dest='extonly', action='store_true', default=False,
+                        help='only use extension to determine file type')
+    parser.add_argument('--exclude', nargs='+', default=[],
+                        help='list of files and directories to exclude from results, relative to repo root')
+    parser.add_argument('--extless-only', dest='extless_only', action='store_true', default=False,
+                        help='only include extensionless files in output')
+    args = parser.parse_args()
+    listing = list_files(targets=args.targets, ftypes=args.ftypes, use_shebang=not args.extonly,
+                         modified_only=args.modified, exclude=args.exclude, extless_only=args.extless_only)
+    for l in listing:
+        print(l)