1 files changed, 112 insertions, 0 deletions
diff --git a/pager.c b/pager.c
new file mode 100644
index 0000000000..975955ba82
--- /dev/null
+++ b/pager.c
@@ -0,0 +1,112 @@
+#include "cache.h"
+#include "run-command.h"
+#include "sigchain.h"
+
+#ifndef DEFAULT_PAGER
+#define DEFAULT_PAGER "less"
+#endif
+
+/*
+ * This is split up from the rest of git so that we can do
+ * something different on Windows.
+ */
+
+#ifndef WIN32
+static void pager_preexec(void)
+{
+	/*
+	 * Work around bug in "less" by not starting it until we
+	 * have real input
+	 */
+	fd_set in;
+
+	FD_ZERO(&in);
+	FD_SET(0, &in);
+	select(1, &in, NULL, &in, NULL);
+}
+#endif
+
+static const char *pager_argv[] = { NULL, NULL };
+static struct child_process pager_process;
+
+static void wait_for_pager(void)
+{
+	fflush(stdout);
+	fflush(stderr);
+	/* signal EOF to pager */
+	close(1);
+	close(2);
+	finish_command(&pager_process);
+}
+
+static void wait_for_pager_signal(int signo)
+{
+	wait_for_pager();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
+const char *git_pager(int stdout_is_tty)
+{
+	const char *pager;
+
+	if (!stdout_is_tty)
+		return NULL;
+
+	pager = getenv("GIT_PAGER");
+	if (!pager) {
+		if (!pager_program)
+			git_config(git_default_config, NULL);
+		pager = pager_program;
+	}
+	if (!pager)
+		pager = getenv("PAGER");
+	if (!pager)
+		pager = DEFAULT_PAGER;
+	else if (!*pager || !strcmp(pager, "cat"))
+		pager = NULL;
+
+	return pager;
+}
+
+void setup_pager(void)
+{
+	const char *pager = git_pager(isatty(1));
+
+	if (!pager)
+		return;
+
+	setenv("GIT_PAGER_IN_USE", "true", 1);
+
+	/* spawn the pager */
+	pager_argv[0] = pager;
+	pager_process.use_shell = 1;
+	pager_process.argv = pager_argv;
+	pager_process.in = -1;
+	if (!getenv("LESS")) {
+		static const char *env[] = { "LESS=FRSX", NULL };
+		pager_process.env = env;
+	}
+#ifndef WIN32
+	pager_process.preexec_cb = pager_preexec;
+#endif
+	if (start_command(&pager_process))
+		return;
+
+	/* original process continues, but writes to the pipe */
+	dup2(pager_process.in, 1);
+	if (isatty(2))
+		dup2(pager_process.in, 2);
+	close(pager_process.in);
+
+	/* this makes sure that the parent terminates after the pager */
+	sigchain_push_common(wait_for_pager_signal);
+	atexit(wait_for_pager);
+}
+
+int pager_in_use(void)
+{
+	const char *env;
+	env = getenv("GIT_PAGER_IN_USE");
+	return env ? git_config_bool("GIT_PAGER_IN_USE", env) : 0;
+}