[PATCH v3 0/4] builtin add -p: hopefully final readkey fixes

[Phillip Wood <phillip.wood123@gmail.com>]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

Thanks to Ævar, Carlo and Dscho for their comments on V2.
Changes since V2:
 * Patch 1
   - fix save_term() prototype (thanks to Carlo)
 * Patch 2
   - avoid closing tty_fd if it is stdin
 * Patch 3
   - removed redundant #include (thanks to Ævar)
   - handle select() timeout correctly
 * Patch 4
   - reset job signals if settcattr() fails

These patches are based on a merge of pw/single-key-interactive and
master. There are a couple of simple textual conflicts with
'cb/save-term-across-editor-invocation' and unfortunately some
semantic conflicts as well. A diff on top of the textual resolution
which handles the semantic conflicts is given after the range-diff at
the end of this message.

V2 Cover Letter:

Thanks to Ramsay and Ævar for their comments on V1.
Changes since V1:
 * Patch 1
   - use an enum for save_term()'s flags (suggested by Ævar)
   - fixed argument order in the windows code (thanks to Ramsay)
 * Patch 2
   - fixed a typo in a comment (thanks to Ramsay)
 * Patch 4
   - stopped duplicating the strings returned by gettext() (suggested by
     Ævar)
   - reworked error message handling in the signal handler to add an
     "error: " prefix (suggested by Ævar)
   - tweaked the background resume error message

V1 Cover Letter:

Fix the remaining issues that I'm aware of when using the built in
"add -p" with interactive.singlekey that are stopping it from being
merged to master. The first three patches make sure that we call
tcsetattr() and the same file descriptor that we use for read() and
work around poll() being broken when reading from terminals on
macos. The final patch is more of an improvement rather than a bug fix
(the same issue already exists in the perl version) and could proceed
separately.

Unfortunately these patches conflict with
'cb/save-term-across-editor-invocation' as well as the textual
conflicts there is a semantic conflict as the argument to save_term()
is changed so the code in editor.c will need updating.

These patches are based on 'pw/single-key-interactive'

Phillip Wood (4):
  terminal: use flags for save_term()
  terminal: don't assume stdin is /dev/tty
  terminal: work around macos poll() bug
  terminal: restore settings on SIGTSTP

 compat/terminal.c | 226 +++++++++++++++++++++++++++++++++++++++-------
 compat/terminal.h |   9 +-
 2 files changed, 202 insertions(+), 33 deletions(-)

Range-diff against v2:
1:  fac5a0f5b7 ! 1:  2c4c5424d7 terminal: use flags for save_term()
    @@ compat/terminal.h
       * failure.
       */
     -int save_term(int full_duplex);
    -+int save_term(unsigned flags);
    ++int save_term(enum save_term_flags flags);
      /* Restore the terminal attributes that were saved with save_term() */
      void restore_term(void);
      
2:  bf29460ec6 ! 2:  cf9275c40c terminal: don't assume stdin is /dev/tty
    @@ Commit message
         Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
     
      ## compat/terminal.c ##
    -@@ compat/terminal.c: void restore_term(void)
    +@@ compat/terminal.c: static void restore_term_on_signal(int sig)
    + static int term_fd = -1;
    + static struct termios old_term;
    + 
    ++static void close_term_fd(void)
    ++{
    ++	if (term_fd)
    ++		close(term_fd);
    ++	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();
    + }
    + 
      int save_term(enum save_term_flags flags)
      {
      	if (term_fd < 0)
    @@ compat/terminal.c: void restore_term(void)
      	if (term_fd < 0)
      		return -1;
      	if (tcgetattr(term_fd, &old_term) < 0)
    +@@ compat/terminal.c: static int disable_bits(enum save_term_flags flags, tcflag_t bits)
    + 
    + 	sigchain_pop_common();
    + error:
    +-	close(term_fd);
    +-	term_fd = -1;
    ++	close_term_fd();
    + 	return -1;
    + }
    + 
     @@ compat/terminal.c: int read_key_without_echo(struct strbuf *buf)
      	static int warning_displayed;
      	int ch;
3:  1815606e82 ! 3:  4828d63ce5 terminal: work around macos poll() bug
    @@ compat/terminal.c: static int enable_non_canonical(enum save_term_flags flags)
     + * On macos it is not possible to use poll() with a terminal so use select
     + * instead.
     + */
    -+#include <sys/select.h>
     +static int getchar_with_timeout(int timeout)
     +{
     +	struct timeval tv, *tvp = NULL;
    @@ compat/terminal.c: static int enable_non_canonical(enum save_term_flags flags)
     +	FD_ZERO(&readfds);
     +	FD_SET(0, &readfds);
     +	res = select(1, &readfds, NULL, NULL, tvp);
    -+	if (res < 0)
    ++	if (res <= 0)
     +		return EOF;
     +
     +	return getchar();
    @@ compat/terminal.c: int read_key_without_echo(struct strbuf *buf)
     -			ch = getchar();
     +			ch = getchar_with_timeout(500);
      			if (ch == EOF)
    - 				return 0;
    + 				break;
      			strbuf_addch(buf, ch);
4:  dd0e1fabb1 ! 4:  3185bc5223 terminal: restore settings on SIGTSTP
    @@ compat/terminal.c: static void restore_term_on_signal(int sig)
     +	errno = saved_errno;
     +}
     +
    - void restore_term(void)
    - {
    - 	if (term_fd < 0)
    -@@ compat/terminal.c: void restore_term(void)
    - 	close(term_fd);
    - 	term_fd = -1;
    - 	sigchain_pop_common();
    ++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)
    +@@ compat/terminal.c: void restore_term(void)
    + 	tcsetattr(term_fd, TCSAFLUSH, &old_term);
    + 	close_term_fd();
    + 	sigchain_pop_common();
    ++	reset_job_signals();
      }
      
      int save_term(enum save_term_flags flags)
    @@ compat/terminal.c: int save_term(enum save_term_flags flags)
      
      	return 0;
      }
    +@@ compat/terminal.c: static int disable_bits(enum save_term_flags flags, tcflag_t bits)
    + 		return 0;
    + 
    + 	sigchain_pop_common();
    ++	reset_job_signals();
    + error:
    + 	close_term_fd();
    + 	return -1;
     @@ compat/terminal.c: static int getchar_with_timeout(int timeout)
      	fd_set readfds;
      	int res;
    @@ compat/terminal.c: static int getchar_with_timeout(int timeout)
      	FD_ZERO(&readfds);
      	FD_SET(0, &readfds);
      	res = select(1, &readfds, NULL, NULL, tvp);
    --	if (res < 0)
    --		return EOF;
    +-	if (res <= 0)
    ++	if (!res)
    + 		return EOF;
     -
     +	if (res < 0) {
     +		if (errno == EINTR)

Semantic conflict resolution:
---- >8 ----
diff --git a/compat/terminal.c b/compat/terminal.c
index bffb1340ab..9a64b9a431 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c
@@ -150,9 +150,8 @@ int save_term(enum save_term_flags flags)
                                                    : open("/dev/tty", O_RDWR);
        if (term_fd < 0)
                return -1;
-       if (full_duplex && !is_controlling_terminal(term_fd)) {
-               close(term_fd);
-               term_fd = -1;
+       if (flags & SAVE_TERM_DUPLEX && !is_controlling_terminal(term_fd)) {
+               close_term_fd();
                return -1;
        }
        if (tcgetattr(term_fd, &old_term) < 0)
diff --git a/editor.c b/editor.c
index 6c5c95e6a2..192d6ea75d 100644
--- a/editor.c
+++ b/editor.c
@@ -55,7 +55,7 @@ static int prepare_term(const char *editor)

        git_config_get_bool("editor.stty", &need_saverestore);
        if (need_saverestore)
-               return save_term(1);
+               return save_term(SAVE_TERM_DUPLEX);
        return 0;
 }

-- 
2.35.1