Add pr2relnotes tool to generate release notes

pr2relnotes takes merged PRs from the git log and generates
formatted release notes including links to the PRs themselves

.gitignore

@@ -18,3 +18,4 @@ logs
 priv/templates/*.dtl.erl
 ebin
 .edts
+env

pr2relnotes.py

@@ -0,0 +1,188 @@
+#!/usr/bin/env python
+
+## Install info
+##   $ virtualenv env
+##   $ source env/bin/activate
+##   $ pip install PyGithub
+##
+## Examples:
+##   Find the differences from last tag to current
+##   $ pr2relnotes.py alpha-6 HEAD
+
+import argparse
+import re
+import os
+import subprocess
+from github import Github
+from github import GithubException
+
+
+def dprint(*args):
+    if VERBOSE:
+        print str(args)
+
+def get_args():
+    """
+    Get command line arguments
+    """
+    parser = argparse.ArgumentParser(description="Find the PR's between two versions")
+    parser.add_argument("old", help = "old version to use")
+    parser.add_argument("new", help = "new version to use")
+    parser.add_argument("-v", "--verbose", help="Enable debug output",
+                        default=False,
+                        action="store_true")
+    parser.add_argument("-f", "--file",
+                        help="Output file to store results (default: tagdiff.md)",
+                        default="tagdiff.md")
+    return parser.parse_args()
+
+def search_prs(log):
+    """
+    Search lines of text for PR numbers
+    """
+    # Find all matches using regex iterator, using the PR # as the group match
+    resultlist = [str(m.group(1)) for m in re.finditer(r"erge pull request #(\d+)", log)]
+    return sorted(resultlist)
+
+def get_env(env):
+    return os.environ[env]
+
+def get_formatted_issue(repo, issue, title, url):
+    """
+    Single place to adjust formatting output of PR data
+    """
+    # Newline support writelines() call which doesn't add newlines
+    # on its own
+    return("* {}/{}: [{}]({})\n".format(repo, issue, title, url))
+
+def gh_get_issue_output(org, repo, issuenum):
+    """
+    Look up PR information using the GitHub api
+    """
+    # Attempt to look up the PR, and don't take down the whole
+    # shebang if a API call fails
+    # This will fail often on forks who don't have the
+    # PRs numbers associated with the forked account
+    # Return empty string on error
+    try:
+        repoObj = gh.get_repo(org + "/" + repo)
+        issue = repoObj.get_issue(int(issuenum))
+        title = issue.title
+        html_url = issue.html_url
+    except GithubException as e:
+        print "Github error({0}): {1}".format(e.status, e.data)
+        return ""
+    except:
+        print "Some github error"
+        return ""
+
+    return(get_formatted_issue(repo, issuenum, title, html_url))
+
+
+def get_org(repourl):
+    """
+    Simple function to parse the organization out of a GitHub URL
+    """
+    dprint("Current repourl to search: " + repourl)
+    # GitHub URLs can be:
+    #    http[s]://www.github.com/org/repo
+    # or           git@github.com:/org/repo
+    pattern = re.compile(r"github.com[/:]+(\w+)/")
+    m = re.search(pattern, repourl)
+    # Fail fast if this is wrong so we can add a pattern to the search
+    if m:
+        return m.group(1)
+    else:
+        raise Exception("Incorrect regex pattern finding repo org")
+
+def get_name(repourl):
+    """
+    Simple function to parse the repository name out of a GitHub URL
+    """
+    dprint("Current repourl to search: " + repourl)
+    repo_pattern = re.compile(r"github.com[/:]\w+/(\w+)")
+    m = re.search(repo_pattern, repourl)
+    if m:
+        return m.group(1)
+    else:
+        raise Exception("Incorrect rexex pattern finding repo url")
+
+def get_repo_url_from_remote():
+    """
+    Function that gets the repository URL from the `git remote` listing
+    """
+    git_remote_bytes = subprocess.check_output(["git", "remote", "-v"])
+    # check_output returns the command results in raw byte format
+    remote_string = git_remote_bytes.decode('utf-8')
+
+    pattern = re.compile(r"github.com[/:]\w+/\w+")
+    m = re.search(pattern, remote_string)
+    if m:
+        return m.group(0)
+    else:
+        raise Exception("Incorrect rexex pattern finding repo url")
+
+def process_log(gitlog, repo_url):
+    """
+    Handles the processing of the gitlog and returns a list
+    of PRs already formatted for output
+    """
+    pr_list = search_prs(gitlog)
+    repoorg = get_org(repo_url)
+    reponame = get_name(repo_url)
+    pr_buffer = []
+    for issue in pr_list:
+            pr_buffer.append(gh_get_issue_output(repoorg, reponame, issue))
+
+    return pr_buffer
+
+def fetch_log(old_ver, new_ver):
+    """
+    Function that processes the git log between the old and new versions
+    """
+    dprint("Current working directory", os.getcwd())
+    gitlogbytes = subprocess.check_output(["git", "log",
+                                           str(old_ver + ".." + new_ver)])
+    return gitlogbytes.decode('utf-8')
+
+
+def compare_versions(repo_url, old_ver, new_ver):
+    # Formatted list of all PRs for all repos
+    pr_out = []
+    gitlog = fetch_log(old_ver, new_ver)
+    pr_out.extend(process_log(gitlog, repo_url))
+    return pr_out
+
+def main():
+    args = get_args()
+
+    # Setup the GitHub object for later use
+    global gh
+    gh = Github(get_env("GHAUTH"))
+
+    if gh == "":
+        raise Exception("Env var GHAUTH must be set to a valid GitHub API key")
+
+    if args.verbose:
+        global VERBOSE
+        VERBOSE=True
+
+    dprint("Inspecting difference in between: ", args.old, " and ", args.new)
+
+    # Find the github URL of the repo we are operating on
+    repo_url = get_repo_url_from_remote()
+
+    # Compare old and new versions
+    pr_list = compare_versions(repo_url, args.old, args.new)
+
+    # Writeout PR listing
+    print "Writing output to file %s" % args.file
+    with open(args.file, 'w') as output:
+        output.writelines(pr_list)
+
+
+if __name__ == "__main__":
+    VERBOSE=False
+    gh=None
+    topdir=os.getcwd()
+    main()