Merge branch 'pw/add-p-single-key'

Finishing touches to C rewrite of "git add -i" in single-key
interactive mode.

* pw/add-p-single-key:
  terminal: restore settings on SIGTSTP
  terminal: work around macos poll() bug
  terminal: don't assume stdin is /dev/tty
  terminal: use flags for save_term()

Author: gitster

compat/terminal.c

@@ -1,4 +1,4 @@
-#include "git-compat-util.h"
+#include "cache.h"
 #include "compat/terminal.h"
 #include "sigchain.h"
 #include "strbuf.h"
@@ -20,39 +20,171 @@ static void restore_term_on_signal(int sig)
 #define INPUT_PATH "/dev/tty"
 #define OUTPUT_PATH "/dev/tty"
 
+static volatile sig_atomic_t term_fd_needs_closing;
 static int term_fd = -1;
 static struct termios old_term;
 
+static const char *background_resume_msg;
+static const char *restore_error_msg;
+static volatile sig_atomic_t ttou_received;
+
+/* async safe error function for use by signal handlers. */
+static void write_err(const char *msg)
+{
+	write_in_full(2, "error: ", strlen("error: "));
+	write_in_full(2, msg, strlen(msg));
+	write_in_full(2, "\n", 1);
+}
+
+static void print_background_resume_msg(int signo)
+{
+	int saved_errno = errno;
+	sigset_t mask;
+	struct sigaction old_sa;
+	struct sigaction sa = { .sa_handler = SIG_DFL };
+
+	ttou_received = 1;
+	write_err(background_resume_msg);
+	sigaction(signo, &sa, &old_sa);
+	raise(signo);
+	sigemptyset(&mask);
+	sigaddset(&mask, signo);
+	sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	/* Stopped here */
+	sigprocmask(SIG_BLOCK, &mask, NULL);
+	sigaction(signo, &old_sa, NULL);
+	errno = saved_errno;
+}
+
+static void restore_terminal_on_suspend(int signo)
+{
+	int saved_errno = errno;
+	int res;
+	struct termios t;
+	sigset_t mask;
+	struct sigaction old_sa;
+	struct sigaction sa = { .sa_handler = SIG_DFL };
+	int can_restore = 1;
+
+	if (tcgetattr(term_fd, &t) < 0)
+		can_restore = 0;
+
+	if (tcsetattr(term_fd, TCSAFLUSH, &old_term) < 0)
+		write_err(restore_error_msg);
+
+	sigaction(signo, &sa, &old_sa);
+	raise(signo);
+	sigemptyset(&mask);
+	sigaddset(&mask, signo);
+	sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	/* Stopped here */
+	sigprocmask(SIG_BLOCK, &mask, NULL);
+	sigaction(signo, &old_sa, NULL);
+	if (!can_restore) {
+		write_err(restore_error_msg);
+		goto out;
+	}
+	/*
+	 * If we resume in the background then we receive SIGTTOU when calling
+	 * tcsetattr() below. Set up a handler to print an error message in that
+	 * case.
+	 */
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGTTOU);
+	sa.sa_mask = old_sa.sa_mask;
+	sa.sa_handler = print_background_resume_msg;
+	sa.sa_flags = SA_RESTART;
+	sigaction(SIGTTOU, &sa, &old_sa);
+ again:
+	ttou_received = 0;
+	sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	res = tcsetattr(term_fd, TCSAFLUSH, &t);
+	sigprocmask(SIG_BLOCK, &mask, NULL);
+	if (ttou_received)
+		goto again;
+	else if (res < 0)
+		write_err(restore_error_msg);
+	sigaction(SIGTTOU, &old_sa, NULL);
+ out:
+	errno = saved_errno;
+}
+
+static void reset_job_signals(void)
+{
+	if (restore_error_msg) {
+		signal(SIGTTIN, SIG_DFL);
+		signal(SIGTTOU, SIG_DFL);
+		signal(SIGTSTP, SIG_DFL);
+		restore_error_msg = NULL;
+		background_resume_msg = NULL;
+	}
+}
+
+static void close_term_fd(void)
+{
+	if (term_fd_needs_closing)
+		close(term_fd);
+	term_fd_needs_closing = 0;
+	term_fd = -1;
+}
+
 void restore_term(void)
 {
 	if (term_fd < 0)
 		return;
 
 	tcsetattr(term_fd, TCSAFLUSH, &old_term);
-	close(term_fd);
-	term_fd = -1;
+	close_term_fd();
 	sigchain_pop_common();
+	reset_job_signals();
 }
 
-int save_term(int full_duplex)
+int save_term(enum save_term_flags flags)
 {
+	struct sigaction sa;
+
 	if (term_fd < 0)
-		term_fd = open("/dev/tty", O_RDWR);
+		term_fd = ((flags & SAVE_TERM_STDIN)
+			   ? 0
+			   : open("/dev/tty", O_RDWR));
 	if (term_fd < 0)
 		return -1;
-	if (tcgetattr(term_fd, &old_term) < 0)
+	term_fd_needs_closing = !(flags & SAVE_TERM_STDIN);
+	if (tcgetattr(term_fd, &old_term) < 0) {
+		close_term_fd();
 		return -1;
+	}
 	sigchain_push_common(restore_term_on_signal);
+	/*
+	 * If job control is disabled then the shell will have set the
+	 * disposition of SIGTSTP to SIG_IGN.
+	 */
+	sigaction(SIGTSTP, NULL, &sa);
+	if (sa.sa_handler == SIG_IGN)
+		return 0;
+
+	/* avoid calling gettext() from signal handler */
+	background_resume_msg = _("cannot resume in the background, please use 'fg' to resume");
+	restore_error_msg = _("cannot restore terminal settings");
+	sa.sa_handler = restore_terminal_on_suspend;
+	sa.sa_flags = SA_RESTART;
+	sigemptyset(&sa.sa_mask);
+	sigaddset(&sa.sa_mask, SIGTSTP);
+	sigaddset(&sa.sa_mask, SIGTTIN);
+	sigaddset(&sa.sa_mask, SIGTTOU);
+	sigaction(SIGTSTP, &sa, NULL);
+	sigaction(SIGTTIN, &sa, NULL);
+	sigaction(SIGTTOU, &sa, NULL);
 
 	return 0;
 }
 
-static int disable_bits(tcflag_t bits)
+static int disable_bits(enum save_term_flags flags, tcflag_t bits)
 {
 	struct termios t;
 
-	if (save_term(0) < 0)
-		goto error;
+	if (save_term(flags) < 0)
+		return -1;
 
 	t = old_term;
 
@@ -65,20 +197,50 @@ static int disable_bits(tcflag_t bits)
 		return 0;
 
 	sigchain_pop_common();
-error:
-	close(term_fd);
-	term_fd = -1;
+	reset_job_signals();
+	close_term_fd();
 	return -1;
 }
 
-static int disable_echo(void)
+static int disable_echo(enum save_term_flags flags)
 {
-	return disable_bits(ECHO);
+	return disable_bits(flags, ECHO);
 }
 
-static int enable_non_canonical(void)
+static int enable_non_canonical(enum save_term_flags flags)
 {
-	return disable_bits(ICANON | ECHO);
+	return disable_bits(flags, ICANON | ECHO);
+}
+
+/*
+ * On macos it is not possible to use poll() with a terminal so use select
+ * instead.
+ */
+static int getchar_with_timeout(int timeout)
+{
+	struct timeval tv, *tvp = NULL;
+	fd_set readfds;
+	int res;
+
+ again:
+	if (timeout >= 0) {
+		tv.tv_sec = timeout / 1000;
+		tv.tv_usec = (timeout % 1000) * 1000;
+		tvp = &tv;
+	}
+
+	FD_ZERO(&readfds);
+	FD_SET(0, &readfds);
+	res = select(1, &readfds, NULL, NULL, tvp);
+	if (!res)
+		return EOF;
+	if (res < 0) {
+		if (errno == EINTR)
+			goto again;
+		else
+			return EOF;
+	}
+	return getchar();
 }
 
 #elif defined(GIT_WINDOWS_NATIVE)
@@ -126,15 +288,15 @@ void restore_term(void)
 	hconin = hconout = INVALID_HANDLE_VALUE;
 }
 
-int save_term(int full_duplex)
+int save_term(enum save_term_flags flags)
 {
 	hconin = CreateFileA("CONIN$", GENERIC_READ | GENERIC_WRITE,
 	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
 	    FILE_ATTRIBUTE_NORMAL, NULL);
 	if (hconin == INVALID_HANDLE_VALUE)
 		return -1;
 
-	if (full_duplex) {
+	if (flags & SAVE_TERM_DUPLEX) {
 		hconout = CreateFileA("CONOUT$", GENERIC_READ | GENERIC_WRITE,
 			FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
 			FILE_ATTRIBUTE_NORMAL, NULL);
@@ -154,7 +316,7 @@ int save_term(int full_duplex)
 	return -1;
 }
 
-static int disable_bits(DWORD bits)
+static int disable_bits(enum save_term_flags flags, DWORD bits)
 {
 	if (use_stty) {
 		struct child_process cp = CHILD_PROCESS_INIT;
@@ -191,7 +353,7 @@ static int disable_bits(DWORD bits)
 		use_stty = 0;
 	}
 
-	if (save_term(0) < 0)
+	if (save_term(flags) < 0)
 		return -1;
 
 	if (!SetConsoleMode(hconin, cmode_in & ~bits)) {
@@ -204,14 +366,15 @@ static int disable_bits(DWORD bits)
 	return 0;
 }
 
-static int disable_echo(void)
+static int disable_echo(enum save_term_flags flags)
 {
-	return disable_bits(ENABLE_ECHO_INPUT);
+	return disable_bits(flags, ENABLE_ECHO_INPUT);
 }
 
-static int enable_non_canonical(void)
+static int enable_non_canonical(enum save_term_flags flags)
 {
-	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
+	return disable_bits(flags,
+			    ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
 /*
@@ -245,6 +408,16 @@ static int mingw_getchar(void)
 }
 #define getchar mingw_getchar
 
+static int getchar_with_timeout(int timeout)
+{
+	struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+	if (poll(&pfd, 1, timeout) < 1)
+		return EOF;
+
+	return getchar();
+}
+
 #endif
 
 #ifndef FORCE_TEXT
@@ -267,7 +440,7 @@ char *git_terminal_prompt(const char *prompt, int echo)
 		return NULL;
 	}
 
-	if (!echo && disable_echo()) {
+	if (!echo && disable_echo(0)) {
 		fclose(input_fh);
 		fclose(output_fh);
 		return NULL;
@@ -361,7 +534,7 @@ int read_key_without_echo(struct strbuf *buf)
 	static int warning_displayed;
 	int ch;
 
-	if (warning_displayed || enable_non_canonical() < 0) {
+	if (warning_displayed || enable_non_canonical(SAVE_TERM_STDIN) < 0) {
 		if (!warning_displayed) {
 			warning("reading single keystrokes not supported on "
 				"this platform; reading line instead");
@@ -395,12 +568,7 @@ int read_key_without_echo(struct strbuf *buf)
 		 * half a second when we know that the sequence is complete.
 		 */
 		while (!is_known_escape_sequence(buf->buf)) {
-			struct pollfd pfd = { .fd = 0, .events = POLLIN };
-
-			if (poll(&pfd, 1, 500) < 1)
-				break;
-
-			ch = getchar();
+			ch = getchar_with_timeout(500);
 			if (ch == EOF)
 				break;
 			strbuf_addch(buf, ch);
@@ -413,10 +581,10 @@ int read_key_without_echo(struct strbuf *buf)
 
 #else
 
-int save_term(int full_duplex)
+int save_term(enum save_term_flags flags)
 {
-	/* full_duplex == 1, but no support available */
-	return -full_duplex;
+	/* no duplex support available */
+	return -!!(flags & SAVE_TERM_DUPLEX);
 }
 
 void restore_term(void)

compat/terminal.h

@@ -1,14 +1,21 @@
 #ifndef COMPAT_TERMINAL_H
 #define COMPAT_TERMINAL_H
 
+enum save_term_flags {
+	/* Save input and output settings */
+	SAVE_TERM_DUPLEX = 1 << 0,
+	/* Save stdin rather than /dev/tty (fails if stdin is not a terminal) */
+	SAVE_TERM_STDIN  = 1 << 1,
+};
+
 /*
  * Save the terminal attributes so they can be restored later by a
  * call to restore_term(). Note that every successful call to
  * save_term() must be matched by a call to restore_term() even if the
  * attributes have not been changed. Returns 0 on success, -1 on
  * failure.
  */
-int save_term(int full_duplex);
+int save_term(enum save_term_flags flags);
 /* Restore the terminal attributes that were saved with save_term() */
 void restore_term(void);