Add dist-hook to create ChangeLog from the commit log,

and to conver the man pages to PDF and plain text, which
may be convenient to those who cannot render man pages.

Makefile.am

@@ -27,6 +27,37 @@ EXTRA_DIST = \
 
 ACLOCAL_AMFLAGS = -I m4
 
+# List of man pages to conver to PDF and plain text in the dist-hook target.
+manfiles = \
+	src/xzdec/xzdec.1 \
+	src/scripts/xzdiff.1 \
+	src/scripts/xzgrep.1 \
+	src/scripts/xzless.1 \
+	src/scripts/xzmore.1
+
+# Create ChangeLog from output of "git log --date=iso --stat".
+# Convert the man pages to PDF and plain text (ASCII only) formats.
+dist-hook:
+	test -d "$(srcdir)/.git" && type git > /dev/null 2>&1 \
+		&& ( cd "$(srcdir)" && git log --date=iso --stat ) \
+			> "$(distdir)/ChangeLog"
+	if type groff > /dev/null 2>&1 && type ps2pdf > /dev/null 2>&1; then \
+		dest="$(distdir)/doc/man" && \
+		mkdir "$$dest" && \
+		mkdir "$$dest/pdf-a4" "$$dest/pdf-letter" "$$dest/txt" && \
+		for FILE in $(manfiles); do \
+			BASE=`basename $$FILE .1` && \
+			groff -man -t -Tps -P-pa4 < "$(srcdir)/$$FILE" \
+				| ps2pdf - - \
+				> "$$dest/pdf-a4/$$BASE-a4.pdf" && \
+			groff -man -t -Tps -P-pletter < "$(srcdir)/$$FILE" \
+				| ps2pdf - - \
+				> "$$dest/pdf-letter/$$BASE-letter.pdf" && \
+			groff -man -t -Tascii < "$(srcdir)/$$FILE" \
+				| col -bx > "$$dest/txt/$$BASE.txt"; \
+		done; \
+	fi
+
 # This works with GNU tar and gives cleaner package than normal 'make dist'.
 mydist:
 	TAR_OPTIONS='--owner=0 --group=0 --numeric-owner --mode=u+rw,go+r-w' \