Automate maintenance of the THANKS file

THANKS now is automatically maintained for you. It uses git author
data to append people who submitted patches in the past.

For non-commit THANKS, you can still manually edit this file.

This commit removes from the THANKS file the people that appear
as git commit authors since we started committing them after
commit 6c976bd. These removed entries get automatically re-
added by `make`.

Makefile.am

@@ -79,7 +79,15 @@ README.gz: $(top_srcdir)/README
 	-gzip -9 < $< > $@
 
 THANKS.gz: $(top_srcdir)/THANKS
-	-gzip -9 < $< > $@
+	sed -e 's/^#.*//' $< > $<.tmp # strip comments
+	sed -e '/^$$/d' $<.tmp > $<.tmp2  # strip empty lines
+	git shortlog -se 6c976bd..HEAD \
+	 | grep -v @apache.org \
+	 | sed -E 's/^[[:blank:]]{5}[[:digit:]]+[[:blank:]]/ * /' \
+	 >> $<.tmp2 # inject git authors
+	echo '\nFor a list of authors see the `AUTHORS` file.\n' >> $<.tmp2
+	-gzip -9 < $<.tmp2 > $@ # zip
+	rm $<.tmp $<.tmp2 # cleanup
 
 check: dev check-js
 	$(top_builddir)/test/etap/run $(top_srcdir)/test/etap

THANKS

@@ -66,7 +66,6 @@ suggesting improvements or submitting changes. Some of these people are:
  * Lim Yue Chuan <shasderias@gmail.com>
  * David Davis <xantus@xantus.org>
  * Klaus Trainer <klaus.trainer@web.de>
- * Dale Harvey <dale@arandomurl.com>
  * Juuso Väänänen <juuso@vaananen.org>
  * Jeff Zellner <jeff.zellner@gmail.com>
  * Benjamin Young <byoung@bigbluehat.com>
@@ -92,12 +91,10 @@ suggesting improvements or submitting changes. Some of these people are:
  * Simon Leblanc <sim.leblanc+apache@gmail.com>
  * Rogutės Sparnuotos <rogutes@googlemail.com>
  * Gavin McDonald <gmcdonald@apache.org>
- * Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
- * Magnus Hoff <maghoff@gmail.com>
- * Alexander Dorofeev <aka.spin@gmail.com>
- * Anthony S Baker <anthony.s.baker@gmail.com>
- * Ewan McDougall <info@mrloop.com>
- * Adam Lofts <Adam.Lofts@gmail.com>
 
-For a list of authors see the `AUTHORS` file.
+# Dear committer who merges a commit from a non-committer:
+# You don't have to manually maintain the THANKS file anymore (yay!).
+# Non-committer authors get automatically appended to THANKS and
+# moved into THANKS.gz by `make`. This note will be stripped as well.
+# Authors from commit 6c976bd and onwards are auto-inserted.