--- a/taskcluster/taskgraph/util/hash.py
+++ b/taskcluster/taskgraph/util/hash.py
@@ -5,17 +5,21 @@
 from __future__ import absolute_import, print_function, unicode_literals
 from mozbuild.util import memoize
 from mozpack.files import FileFinder
 import mozpack.path as mozpath
 import hashlib
 
 
 @memoize
-def _hash_path(path):
+def hash_path(path):
+    """Hash a single file.
+
+    Returns the SHA-256 hash in hex form.
+    """
     with open(path) as fh:
         return hashlib.sha256(fh.read()).hexdigest()
 
 
 def hash_paths(base_path, patterns):
     """
     Give a list of path patterns, return a digest of the contents of all
     the corresponding files, similarly to git tree objects or mercurial
@@ -30,12 +34,12 @@ def hash_paths(base_path, patterns):
     for pattern in patterns:
         found = list(finder.find(pattern))
         if found:
             files.update(found)
         else:
             raise Exception('%s did not match anything' % pattern)
     for path in sorted(files.keys()):
         h.update('{} {}\n'.format(
-            _hash_path(mozpath.abspath(mozpath.join(base_path, path))),
+            hash_path(mozpath.abspath(mozpath.join(base_path, path))),
             mozpath.normsep(path)
         ))
     return h.hexdigest()