Re: [PATCH 2/3] setup_pager: set MORE=R

From: Jeff King <peff@peff.net>
Date: Jan 21, 2014, 06:13 UTC
Message-ID: <20140121061307.GE5878@sigill.intra.peff.net>
In-Reply-To: <xmqq61piw4yf.fsf@gitster.dls.corp.google.com>

On Fri, Jan 17, 2014 at 03:42:32PM -0800, Junio C Hamano wrote:

Show 12 quoted lines

> Junio C Hamano <gitster@pobox.com> writes:
> 
> > Perhaps we can start it like this.  Then pager.c can iterate over
> > the PAGER_ENV string, parse out LESS=, LV=, etc., and do its thing.
> >
> > We would also need to muck with git-sh-setup.sh but that file is
> > already preprocessed in the Makefile, so we should be able to do
> > something similar to "# @@BROKEN_PATH_FIX@@" there.
> 
> And here is such an attempt.  There may be some missing dependencies
> that need to be covered with a mechanism like GIT-BUILD-OPTIONS,
> though.

Perhaps instead of just dumping it into a macro, we could actually parse it at compile time into C code, and store the result as a header file. Then that header file becomes the proper dependency, and this run-time error:

Show 6 quoted lines

> +	while (*pager_env) {
> +		struct strbuf buf = STRBUF_INIT;
> +		const char *cp = strchrnul(pager_env, '=');
> +
> +		if (!*cp)
> +			die("malformed build-time PAGER_ENV");

would become a compile-time error. We could do the same for the shell code, too.

I'm thinking something like:

diff --git a/Makefile b/Makefile
index b4af1e2..3a8d15e 100644
--- a/Makefile
+++ b/Makefile
@@ -2182,6 +2182,16 @@ GIT-LDFLAGS: FORCE
 		echo "$$FLAGS" >GIT-LDFLAGS; \
             fi
 
+GIT-PAGER-ENV:
+	@PAGER_ENV='$(PAGER_ENV)'; \
+	if test x"$$PAGER_ENV" != x"`cat GIT-PAGER-ENV 2>/dev/null`"; then \
+		echo "$$PAGER_ENV" >GIT-PAGER-ENV; \
+	fi
+
+pager-env.h: GIT-PAGER-ENV mkcarray
+	$(SHELL_PATH) mkcarray pager_env <$< >$@+
+	mv $@+ $@
+
 # We need to apply sq twice, once to protect from the shell
 # that runs GIT-BUILD-OPTIONS, and then again to protect it
 # and the first level quoting from the shell that runs "echo".
diff --git a/mkcarray b/mkcarray
index e69de29..5962440 100644
--- a/mkcarray
+++ b/mkcarray
@@ -0,0 +1,21 @@
+name=$1; shift
+guard=$(echo "$name" | tr a-z A-Z)
+
+cat <<-EOF
+#ifndef ${guard}_H
+#define ${guard}_H
+
+static const char *${name} = {
+EOF
+
+for i in $(cat); do
+	# XXX c-quote the values?
+	printf '\t"%s",\n' "$i"
+done
+
+cat <<EOF
+	NULL
+};
+
+#endif /* ${guard}_H */
+EOF