contrib: Allow use of github API authentication in github-merge

The API request limit for unauthenticated requests is quite low.
I started running into rate limiting errors. The limit
for authenticated requests is much higher.

This patch adds an optional configuration setting `user.ghtoken`
that, when set, is used to authenticate requests to the API.

contrib/devtools/README.md

@@ -119,7 +119,25 @@ Configuring the github-merge tool for the bitcoin repository is done in the foll
 
  git config githubmerge.repository bitcoin/bitcoin
  git config githubmerge.testcmd "make -j4 check" (adapt to whatever you want to use for testing)
- git config --global user.signingkey mykeyid (if you want to GPG sign)
+ git config --global user.signingkey mykeyid
+
+Authentication (optional)
+--------------------------
+
+The API request limit for unauthenticated requests is quite low, but the
+limit for authenticated requests is much higher. If you start running
+into rate limiting errors it can be useful to set an authentication token
+so that the script can authenticate requests.
+
+- First, go to [Personal access tokens](https://github.com/settings/tokens).
+- Click 'Generate new token'.
+- Fill in an arbitrary token description. No further privileges are needed.
+- Click the `Generate token` button at the bottom of the form.
+- Copy the generated token (should be a hexadecimal string)
+
+Then do:
+
+ git config --global user.ghtoken "pasted token"
 
 Create and verify timestamps of merge commits
 ---------------------------------------------

contrib/devtools/github-merge.py

@@ -47,13 +47,15 @@ def git_config_get(option, default=None):
  except subprocess.CalledProcessError:
  return default
 
-def retrieve_pr_info(repo,pull):
+def retrieve_pr_info(repo,pull,ghtoken):
  '''
  Retrieve pull request information from github.
  Return None if no title can be found, or an error happens.
  '''
  try:
  req = Request("https://api.github.com/repos/"+repo+"/pulls/"+pull)
+ if ghtoken is not None:
+ req.add_header('Authorization', 'token ' + ghtoken)
  result = urlopen(req)
  reader = codecs.getreader('utf-8')
  obj = json.load(reader(result))
@@ -140,6 +142,7 @@ def parse_arguments():
  In addition, you can set the following git configuration variables:
  githubmerge.repository (mandatory),
  user.signingkey (mandatory),
+ user.ghtoken (default: none).
  githubmerge.host (default: git@github.com),
  githubmerge.branch (no default),
  githubmerge.testcmd (default: none).
@@ -158,6 +161,7 @@ def main():
  host = git_config_get('githubmerge.host','git@github.com')
  opt_branch = git_config_get('githubmerge.branch',None)
  testcmd = git_config_get('githubmerge.testcmd')
+ ghtoken = git_config_get('user.ghtoken')
  signingkey = git_config_get('user.signingkey')
  if repo is None:
  print("ERROR: No repository configured. Use this command to set:", file=stderr)
@@ -178,7 +182,7 @@ def main():
  pull = str(args.pull[0])
 
  # Receive pull information from github
- info = retrieve_pr_info(repo,pull)
+ info = retrieve_pr_info(repo,pull,ghtoken)
  if info is None:
  sys.exit(1)
  title = info['title'].strip()