add script to check for new contributors to list

Use git shortlog to create a list of contributors
that are not yet included in CONTRIBUTORS.rst

The email address is taken as definitive.
People with the same name, but different email addresses
are supported.
Aliases, different email addresses for the same person,
are handled by git with .mailmap

.mailmap

@@ -0,0 +1,2 @@
+Andrew Brown <brownan@gmail.com> <andrew@fry.(none)>
+Alex Headley <aheadley@waysaboutstuff.com> <aheadley@nexcess.net>

contrib/contributors.py

@@ -0,0 +1,51 @@
+#!/usr/bin/python2
+"""List contributors that are not yet in the contributor list
+
+Alias handling is done by git with .mailmap
+"""
+
+import sys
+from subprocess import Popen, PIPE
+
+def main():
+    if len(sys.argv) > 1:
+        branch = sys.argv[1]
+    else:
+        branch = "master"
+
+    contributors=[]
+    p_git = Popen(["git", "shortlog", "-se", branch], stdout=PIPE)
+    for line in p_git.stdout:
+        contributors.append({
+            'count': int(line.split("\t")[0].strip()),
+            'name': line.split("\t")[1].split()[0:-1],
+            'email': line.split("\t")[1].split()[-1]
+            })
+
+    old_contributors=[]
+    with open("CONTRIBUTORS.rst", "r") as contrib_file:
+        for line in contrib_file:
+            if "@" in line:
+                old_contributors.append({
+                    'name': line.split()[1:-1],
+                    'email': line.split()[-1]
+                    })
+    # We don't access the name of old/listed contributors at all
+    # but that might change.
+    # So we parse it anyways and strip it off again.
+    old_emails = map(lambda x: x['email'], old_contributors)
+
+    new_contributors=[]
+    for contributor in contributors:
+        if contributor["email"] not in old_emails:
+            new_contributors.append(contributor)
+
+    # sort on the last word of the name
+    new_contributors = sorted(new_contributors,
+            key=lambda x: x['name'][-1].lower())
+    for contributor in new_contributors:
+        print "{0:3d} {1:25s} {2}".format(contributor["count"],
+                " ".join(contributor["name"]), contributor["email"])
+
+if __name__ == "__main__":
+    main()