diff --git a/README b/README.md
similarity index 85%
rename from README
rename to README.md
index 57cf1be..034da43 100644
--- a/README
+++ b/README.md
@@ -8,7 +8,7 @@ TripleO (or other gerrit based projects).
  - some example inputs for doing rack testing of tripleo in the rack-testing
    subdir
 
-To use:
+## Usage
 
 * create a repo_refs.yaml in your TRIPLEO_ROOT (see the one in the root of this
   repository for inspiration).
@@ -18,7 +18,10 @@ To use:
 
 * run prep_source_repos $YOUR\_REFS\_FILE $TRIPLEO\_ROOT to checkout and update
   the repositories specified by the refs file. Note that local edits are saved
-  via git stash whenever you refresh your source repos.
+  via git stash whenever you refresh your source repos, and restored after the
+  update (which may, of course, fail). This provides a convenient way to use
+  local edits / work in progress for repositories that are used directly (vs
+  e.g. those that are cloned into images).
 
 * source YOUR_REFS_FILE.variables to configure TripleO scripts to use your
   freshly integrated branches
diff --git a/bin/prep_source_repos b/bin/prep_source_repos
index a9bcf8b..53ee08e 100755
--- a/bin/prep_source_repos
+++ b/bin/prep_source_repos
@@ -81,7 +81,9 @@ def main():
                 else:
                     components.append(ref)
             branch_name = 'rollup_' + '_'.join(components)
-        check_call(['git', 'stash'], cwd=rd)
+        dirty = check_output(['git', 'status', '-z', '-uno'], cwd=rd)
+        if dirty:
+            check_call(['git', 'stash'], cwd=rd)
         branches = check_output(['git', 'branch', '-a'], cwd=rd)
         if ' ' + branch_name in branches:
             print 'Resetting existing branch %s...' % branch_name
@@ -93,6 +95,8 @@ def main():
             if len(ref.split('/')) == 3:
                 ref = 'refs/changes/%s' % ref
             check_call(['git', 'merge', '--no-edit', ref], cwd=rd)
+        if dirty:
+            check_call(['git', 'stash', 'pop'], cwd=rd)
         normalised_repo = re.sub('[^A-Za-z0-9_]', '_', repo)
         if repo not in CONF['gerrit_refs']:
             print 'no refs for %s' % repo