1 files changed, 250 insertions, 0 deletions
diff --git a/pager.c b/pager.c
new file mode 100644
index 000000000000..41446d4f0543
--- /dev/null
+++ b/pager.c
@@ -0,0 +1,250 @@
+#include "cache.h"
+#include "config.h"
+#include "run-command.h"
+#include "sigchain.h"
+#include "alias.h"
+
+#ifndef DEFAULT_PAGER
+#define DEFAULT_PAGER "less"
+#endif
+
+static struct child_process pager_process = CHILD_PROCESS_INIT;
+static const char *pager_program;
+
+static void wait_for_pager(int in_signal)
+{
+	if (!in_signal) {
+		fflush(stdout);
+		fflush(stderr);
+	}
+	/* signal EOF to pager */
+	close(1);
+	close(2);
+	if (in_signal)
+		finish_command_in_signal(&pager_process);
+	else
+		finish_command(&pager_process);
+}
+
+static void wait_for_pager_atexit(void)
+{
+	wait_for_pager(0);
+}
+
+static void wait_for_pager_signal(int signo)
+{
+	wait_for_pager(1);
+	sigchain_pop(signo);
+	raise(signo);
+}
+
+static int core_pager_config(const char *var, const char *value, void *data)
+{
+	if (!strcmp(var, "core.pager"))
+		return git_config_string(&pager_program, var, value);
+	return 0;
+}
+
+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)
+			read_early_config(core_pager_config, NULL);
+		pager = pager_program;
+	}
+	if (!pager)
+		pager = getenv("PAGER");
+	if (!pager)
+		pager = DEFAULT_PAGER;
+	if (!*pager || !strcmp(pager, "cat"))
+		pager = NULL;
+
+	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;
+	setup_pager_env(&pager_process->env_array);
+	pager_process->trace2_child_class = "pager";
+}
+
+void setup_pager(void)
+{
+	const char *pager = git_pager(isatty(1));
+
+	if (!pager)
+		return;
+
+	/*
+	 * After we redirect standard output, we won't be able to use an ioctl
+	 * to get the terminal size. Let's grab it now, and then set $COLUMNS
+	 * to communicate it to any sub-processes.
+	 */
+	{
+		char buf[64];
+		xsnprintf(buf, sizeof(buf), "%d", term_columns());
+		setenv("COLUMNS", buf, 0);
+	}
+
+	setenv("GIT_PAGER_IN_USE", "true", 1);
+
+	/* spawn the pager */
+	prepare_pager_args(&pager_process, pager);
+	pager_process.in = -1;
+	argv_array_push(&pager_process.env_array, "GIT_PAGER_IN_USE");
+	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_atexit);
+}
+
+int pager_in_use(void)
+{
+	return git_env_bool("GIT_PAGER_IN_USE", 0);
+}
+
+/*
+ * Return cached value (if set) or $COLUMNS environment variable (if
+ * set and positive) or ioctl(1, TIOCGWINSZ).ws_col (if positive),
+ * and default to 80 if all else fails.
+ */
+int term_columns(void)
+{
+	static int term_columns_at_startup;
+
+	char *col_string;
+	int n_cols;
+
+	if (term_columns_at_startup)
+		return term_columns_at_startup;
+
+	term_columns_at_startup = 80;
+
+	col_string = getenv("COLUMNS");
+	if (col_string && (n_cols = atoi(col_string)) > 0)
+		term_columns_at_startup = n_cols;
+#ifdef TIOCGWINSZ
+	else {
+		struct winsize ws;
+		if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_col)
+			term_columns_at_startup = ws.ws_col;
+	}
+#endif
+
+	return term_columns_at_startup;
+}
+
+/*
+ * Clear the entire line, leave cursor in first column.
+ */
+void term_clear_line(void)
+{
+	if (is_terminal_dumb())
+		/*
+		 * Fall back to print a terminal width worth of space
+		 * characters (hoping that the terminal is still as wide
+		 * as it was upon the first call to term_columns()).
+		 */
+		fprintf(stderr, "\r%*s\r", term_columns(), "");
+	else
+		/*
+		 * On non-dumb terminals use an escape sequence to clear
+		 * the whole line, no matter how wide the terminal.
+		 */
+		fputs("\r\033[K", stderr);
+}
+
+/*
+ * How many columns do we need to show this number in decimal?
+ */
+int decimal_width(uintmax_t number)
+{
+	int width;
+
+	for (width = 1; number >= 10; width++)
+		number /= 10;
+	return width;
+}
+
+struct pager_command_config_data {
+	const char *cmd;
+	int want;
+	char *value;
+};
+
+static int pager_command_config(const char *var, const char *value, void *vdata)
+{
+	struct pager_command_config_data *data = vdata;
+	const char *cmd;
+
+	if (skip_prefix(var, "pager.", &cmd) && !strcmp(cmd, data->cmd)) {
+		int b = git_parse_maybe_bool(value);
+		if (b >= 0)
+			data->want = b;
+		else {
+			data->want = 1;
+			data->value = xstrdup(value);
+		}
+	}
+
+	return 0;
+}
+
+/* returns 0 for "no pager", 1 for "use pager", and -1 for "not specified" */
+int check_pager_config(const char *cmd)
+{
+	struct pager_command_config_data data;
+
+	data.cmd = cmd;
+	data.want = -1;
+	data.value = NULL;
+
+	read_early_config(pager_command_config, &data);
+
+	if (data.value)
+		pager_program = data.value;
+	return data.want;
+}