pager: move pager-specific setup into the build

Allowing PAGER_ENV to be set at build-time allows us to move
pager-specific knowledge out of our build.  This allows us to
set a better default for FreeBSD more(1), which pretends not to
understand ANSI color escapes if the MORE environment variable
is left empty, but accepts the same variables as less(1)

Originally-from:
 https://public-inbox.org/git/xmqq61piw4yf.fsf@gitster.dls.corp.google.com/

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 4 deletions

diff --git a/pager.c b/pager.c
index 4bc0481..6470b81 100644
--- a/pager.c
+++ b/pager.c
@@ -63,14 +63,38 @@ const char *git_pager(int stdout_is_tty)
 	return pager;
 }
 
+static void setup_pager_env(struct argv_array *env)
+{
+	const char **argv;
+	int i;
+	char *pager_env = xstrdup(PAGER_ENV);
+	int n = split_cmdline(pager_env, &argv);
+
+	if (n < 0)
+		die("malformed build-time PAGER_ENV: %s",
+			split_cmdline_strerror(n));
+
+	for (i = 0; i < n; i++) {
+		char *cp = strchr(argv[i], '=');
+
+		if (!cp)
+			die("malformed build-time PAGER_ENV");
+
+		*cp = '\0';
+		if (!getenv(argv[i])) {
+			*cp = '=';
+			argv_array_push(env, argv[i]);
+		}
+	}
+	free(pager_env);
+	free(argv);
+}
+
 void prepare_pager_args(struct child_process *pager_process, const char *pager)
 {
 	argv_array_push(&pager_process->args, pager);
 	pager_process->use_shell = 1;
-	if (!getenv("LESS"))
-		argv_array_push(&pager_process->env_array, "LESS=FRX");
-	if (!getenv("LV"))
-		argv_array_push(&pager_process->env_array, "LV=-c");
+	setup_pager_env(&pager_process->env_array);
 }
 
 void setup_pager(void)