Build website incrementally (and faster if you have the CPU cores)

This is done by replacing www/generate.sh with a Makefile. Benefits:

- Makes builds incremental, meaning that only the minimum number of
  markdown files will be converted to HTML during a build. The previous
  scheme always generated a new HTML file for every markdown file,
  which is a big waste of time if only 1 or 2 markdown files have been
  changed.

- Allows for much faster builds through concurrent jobs (e.g., via
  "make -j4").  On my 4-core machine, my average build time for the
  website with generate.sh was just over 26 seconds; with "make -j4",
  it was 13 seconds.

- Avoids portability issues with find(1) in generate.sh, which I was
  encountering on OpenBSD.

A note on portability: unlike GNU Make, OpenBSD's Make does not have
the "$(shell [commands])" construct, so we don't use that. Instead we
use "!= [commands]", which is supported by both.

1 files changed, 44 insertions, 0 deletions

diff --git a/www/Makefile b/www/Makefile
new file mode 100644
index 00000000..681e3067
--- /dev/null
+++ b/www/Makefile
@@ -0,0 +1,44 @@
+# Copyright (C) 2017 Michael Reed <michael@michaelreed.io>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+MD_MAIN != find -L . -name '*.md' -and ! -path '*/news/*'
+HTML_MAIN = $(MD_MAIN:.md=.html)
+
+MD_NEWS != find -L news -name '*.md' -and ! -name index.md
+HTML_NEWS = $(MD_NEWS:.md=.html)
+
+
+# news/index.html implies the building of $(HTML_NEWS).
+all: $(HTML_MAIN) news/index.html
+
+.SUFFIXES: .md .html
+# Does not apply for news/index.md; see below.
+.md.html:
+	./publish.sh $<
+
+# Unlike all the other markdown files, news/index.md does not exist at first:
+# it must be generated by index.sh. Also note that index.sh depends on the
+# existence of the HTML version of all news items, hence the dependency line
+# below.
+news/index.md: $(HTML_NEWS)
+	./index.sh
+
+clean:
+	rm -f	$(HTML_MAIN) $(HTML_MAIN:.html=.bare.html) \
+		$(HTML_NEWS) $(HTML_NEWS:.html=.bare.html) \
+		news/index.md news/index.html news/index.bare.html \
+		feed.xml news/feed.xml
+
+.PHONY: clean