@matheusbsbs / matheus-bagliano / commits / e8bd8883fe

pager: introduce wait_for_pager

Since f67b45f862 (Introduce trivial new pager.c helper infrastructure, 2006-02-28) we have the machinery to send our output to a pager. That machinery, once set up, does not allow us to regain the original stdio streams. In the interactive commands (i.e.: add -p) we want to use the pager for some output, while maintaining the interaction with the user. Modify the pager machinery so that we can use `setup_pager()` and, once we've finished sending the desired output for the pager, wait for the pager termination using a new function `wait_for_pager()`. Make this function reset the pager machinery before returning. One specific point to note is that we avoid forking the pager in `setup_pager()` if the configured pager is an empty string [*1*] or simply "cat" [*2*]. In these cases, `setup_pager()` does nothing and therefore `wait_for_pager()` should not be called. We could modify `setup_pager()` to return an indication of these situations, so we could avoid calling `wait_for_pager()`. However, let's avoid transferring that responsibility to the caller and instead treat the call to `wait_for_pager()` as a no-op when we know we haven't forked the pager. 1.- 402461aab1 (pager: do not fork a pager if PAGER is set to empty., 2006-04-16) 2.- caef71a535 (Do not fork PAGER=cat, 2006-04-16) Signed-off-by: Rubén Justo <rjusto@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Rubén Justo committed Jul 25, 2024 at 15:44 UTC e8bd8883feb7551f7d1870403d212c77cd56071b

2 files changed +41 -6

pager.c

+40 -6

@@ -14,7 +14,7 @@ int pager_use_color = 1;

15 static struct child_process pager_process;

16 static char *pager_program;

17 -static int close_fd2;

17 +static int old_fd1 = -1, old_fd2 = -1;

19 /* Is the value coming back from term_columns() just a guess? */

20 static int term_columns_guessed;

@@ -24,11 +24,11 @@ static void close_pager_fds(void)

24 {

25 /* signal EOF to pager */

26 close(1);

27 - if (close_fd2)

27 + if (old_fd2 != -1)

28 close(2);

29 }

31 -static void wait_for_pager_atexit(void)

31 +static void finish_pager(void)

32 {

33 fflush(stdout);

34 fflush(stderr);

@@ -36,8 +36,37 @@ static void wait_for_pager_atexit(void)

36 finish_command(&pager_process);

37 }

39 +static void wait_for_pager_atexit(void)

40 +{

41 + if (old_fd1 == -1)

42 + return;

43 +

44 + finish_pager();

45 +}

46 +

47 +void wait_for_pager(void)

48 +{

49 + if (old_fd1 == -1)

50 + return;

51 +

52 + finish_pager();

53 + sigchain_pop_common();

54 + unsetenv("GIT_PAGER_IN_USE");

55 + dup2(old_fd1, 1);

56 + close(old_fd1);

57 + old_fd1 = -1;

58 + if (old_fd2 != -1) {

59 + dup2(old_fd2, 2);

60 + close(old_fd2);

61 + old_fd2 = -1;

62 + }

63 +}

64 +

65 static void wait_for_pager_signal(int signo)

66 {

67 + if (old_fd1 == -1)

68 + return;

69 +

70 close_pager_fds();

71 finish_command_in_signal(&pager_process);

72 sigchain_pop(signo);

@@ -113,6 +142,7 @@ void prepare_pager_args(struct child_process *pager_process, const char *pager)

142

143 void setup_pager(void)

144 {

145 + static int once = 0;

146 const char *pager = git_pager(isatty(1));

147

148 if (!pager)

@@ -142,16 +172,20 @@ void setup_pager(void)

172 die("unable to execute pager '%s'", pager);

173

174 /* original process continues, but writes to the pipe */

175 + old_fd1 = dup(1);

176 dup2(pager_process.in, 1);

177 if (isatty(2)) {

147 - close_fd2 = 1;

178 + old_fd2 = dup(2);

179 dup2(pager_process.in, 2);

180 }

181 close(pager_process.in);

182

152 - /* this makes sure that the parent terminates after the pager */

183 sigchain_push_common(wait_for_pager_signal);

154 - atexit(wait_for_pager_atexit);

184 +

185 + if (!once) {

186 + once++;

187 + atexit(wait_for_pager_atexit);

188 + }

189 }

190

191 int pager_in_use(void)

pager.h

@@ -5,6 +5,7 @@ struct child_process;

6 const char *git_pager(int stdout_is_tty);

7 void setup_pager(void);

8 +void wait_for_pager(void);

9 int pager_in_use(void);

10 int term_columns(void);

11 void term_clear_line(void);