filter: add gravatar scripts

The lua one is hugely faster than the python one, but both are included
for comparison.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

filters/email-gravatar.lua

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+-- This script may be used with the email-filter or repo.email-filter settings in cgitrc.
+-- It adds gravatar icons to author names. It is designed to be used with the lua:
+-- prefix in filters. It is much faster than the corresponding python script.
+--
+-- Requirements:
+-- 	luacrypto >= 0.3
+-- 	<http://mkottman.github.io/luacrypto/>
+--
+
+require("crypto")
+
+function filter_open(email)
+	buffer = ""
+	md5 = crypto.digest("md5", email:sub(2, -2):lower())
+end
+
+function filter_close()
+	html("<img src='//www.gravatar.com/avatar/" .. md5 .. "?s=13&d=retro' style='height:10pt;width:10pt'> " .. buffer)
+end
+
+function filter_write(str)
+	buffer = buffer .. str
+end
+
+

filters/email-gravatar.py

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+#!/usr/bin/env python3
+
+# Please prefer the email-gravatar.lua using lua: as a prefix over this script. This
+# script is very slow, in comparison.
+#
+# This script may be used with the email-filter or repo.email-filter settings in cgitrc.
+#
+# The following environment variables can be used to retrieve the configuration
+# of the repository for which this script is called:
+# CGIT_REPO_URL        ( = repo.url       setting )
+# CGIT_REPO_NAME       ( = repo.name      setting )
+# CGIT_REPO_PATH       ( = repo.path      setting )
+# CGIT_REPO_OWNER      ( = repo.owner     setting )
+# CGIT_REPO_DEFBRANCH  ( = repo.defbranch setting )
+# CGIT_REPO_SECTION    ( = section        setting )
+# CGIT_REPO_CLONE_URL  ( = repo.clone-url setting )
+#
+# It receives an email address on argv[1] and text on stdin. It prints
+# to stdout that text prepended by a gravatar at 10pt.
+
+import sys
+import hashlib
+
+email = sys.argv[1].lower().strip()
+if email[0] == '<':
+        email = email[1:]
+if email[-1] == '>':
+        email = email[0:-1]
+
+md5 = hashlib.md5(email.encode()).hexdigest()
+text = sys.stdin.read().strip()
+
+print("<img src='//www.gravatar.com/avatar/" + md5 + "?s=13&d=retro' style='height:10pt;width:10pt'> " + text)