configure: Generate some documentation into Makefile.config.

It's just not nice to auto-generate a file without helping out the
poor user who gets stuck trying to figure out what went wrong.

diff --git a/configure b/configure
index 97ee606fd3cf51c818e18d97ec1f5e4c8f01e572..92b6710fdef8ff020954e9e01709fca1efb23ee0 100755 (executable)
--- a/configure
+++ b/configure
@@ -161,9 +161,25 @@ EOF
 
 # construct the Makefile.config
 cat > Makefile.config <<EOF
+# This Makefile.config was automatically generated by the ./configure
+# script of notmuch. If the configure script identified anything
+# incorrectly, then you can edit this file to try to correct things,
+# but be warned that if configure is run again it will destroy your
+# changes, (and this could happen by simply calling "make" if the
+# configure script is updated).
+
+# The prefix to which notmuch should be installed
 prefix = /usr/local
+
+# The directory to which emacs lisp files should be installed
 emacs_lispdir=${emacs_lispdir}
+
+# Whether the getline function is available (if not, then notmuch will
+# build its own version)
 HAVE_GETLINE = ${have_getline}
+
+# Various flags needed to compile and link against the dependencies of
+# notmuch.
 override CFLAGS += ${cflags} -DHAVE_VALGRIND=${have_valgrind} -DHAVE_GETLINE=\$(HAVE_GETLINE)
 override CXXFLAGS += ${cflags} ${cxxflags}
 override LDFLAGS += ${ldflags}