reset patched repos before re-syncing

.circleci/config.yml

@@ -218,6 +218,7 @@ step-gclient-sync: &step-gclient-sync
           "$CIRCLE_REPOSITORY_URL"
 
         if ! gclient sync --with_branch_heads --with_tags; then
+          python src/electron/script/reset_patched_repos.py
           if ELECTRON_USE_THREE_WAY_MERGE_FOR_PATCHES=1 gclient sync -f --with_branch_heads --with_tags; then
             # Re-export all the new patches now that they've been nicely 3-way
             # merged

script/lib/git.py

@@ -126,7 +126,7 @@ def reset(repo):
 
 
 def commit(repo, author, message):
-  """ Commit whatever in the index is now."""
+  """Commit whatever in the index is now."""
 
   # Let's setup committer info so git won't complain about it being missing.
   # TODO: Is there a better way to set committer's name and email?
@@ -143,27 +143,33 @@ def commit(repo, author, message):
   committed_successfully = (return_code == 0)
   return committed_successfully
 
+def get_upstream_head(repo):
+  args = [
+    'git',
+    '-C',
+    repo,
+    'rev-parse',
+    '--verify',
+    'refs/patches/upstream-head',
+  ]
+  return subprocess.check_output(args).strip()
+
+def get_commit_count(repo, commit_range):
+  args = [
+    'git',
+    '-C',
+    repo,
+    'rev-list',
+    '--count',
+    commit_range
+  ]
+  return int(subprocess.check_output(args).strip())
+
 def guess_base_commit(repo):
   """Guess which commit the patches might be based on"""
   try:
-    args = [
-      'git',
-      '-C',
-      repo,
-      'rev-parse',
-      '--verify',
-      'refs/patches/upstream-head',
-    ]
-    upstream_head = subprocess.check_output(args).strip()
-    args = [
-      'git',
-      '-C',
-      repo,
-      'rev-list',
-      '--count',
-      upstream_head + '..',
-    ]
-    num_commits = subprocess.check_output(args).strip()
+    upstream_head = get_upstream_head(repo)
+    num_commits = get_commit_count(repo, upstream_head + '..')
     return [upstream_head, num_commits]
   except subprocess.CalledProcessError:
     args = [

script/reset_patched_repos.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+
+import argparse
+import json
+import subprocess
+
+
+def reset_patched_repos(dirs):
+  for patch_dir, repo in dirs.iteritems():
+    args = ['git', '-C', repo, 'am', '--abort']
+    subprocess.call(args) # ignore failure
+    args = ['git', '-C', repo, 'checkout', 'refs/patches/upstream-head']
+    subprocess.call(args) # ignore failure
+
+
+def parse_args():
+  parser = argparse.ArgumentParser(description='Reset patched repos')
+  parser.add_argument('config', nargs='+',
+                      type=argparse.FileType('r'),
+                      help='patches\' config(s) in the JSON format')
+  return parser.parse_args()
+
+
+def main():
+  configs = parse_args().config
+  for config_json in configs:
+    reset_patched_repos(json.load(config_json))
+
+
+if __name__ == '__main__':
+  main()