Use $USERNAME as a fallback for commit

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Use $USERNAME as a fallback for commit

Suggested by Giuseppe Bilotta <[e-mail]>

manifest hash: 3f86a63aebaf6c30eaa3a2081e1e5f9caa20caa1
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mercurial/hg.py

@@ -164,7 +164,9 b' class changelog(revlog):'
         user = (user or
                 os.environ.get("HGUSER") or
                 os.environ.get("EMAIL") or
-                os.environ.get("LOGNAME", "unknown") + '@' + socket.getfqdn())
+                (os.environ.get("LOGNAME",
+                               os.environ.get("USERNAME", "unknown"))
+                 + '@' + socket.getfqdn()))
         date = date or "%d %d" % (time.time(), time.timezone)
         list.sort()
         l = [hex(manifest), user, date] + list + ["", desc]