Merge branch 'pr/use-default-sigpipe-setting'

We used to get confused when a process called us with SIGPIPE
ignored; we do want to die with SIGPIPE when the output is not
read by default, and do ignore the signal when appropriate.

* pr/use-default-sigpipe-setting:
mingw.h: add dummy functions for sigset_t operations
unblock and unignore SIGPIPE

diff --combined git.c
index 4076b014aba6c488e51a9bae8e5cd4b26e4e2476,bf4d41f0e60ba36e56e75bf18137c39a1b8c638f..4cebf32126014938533b66cb57164c6602a1675c
--- 1/git.c
--- 2/git.c
+++ b/git.c
@@@ -14,13 -14,13 +14,13 @@@ const char git_usage_string[] 
        "           <command> [<args>]";
  
  const char git_more_info_string[] =
 -      N_("'git help -a' and 'git help -g' lists available subcommands and some\n"
 +      N_("'git help -a' and 'git help -g' list available subcommands and some\n"
           "concept guides. See 'git help <command>' or 'git help <concept>'\n"
           "to read about a specific subcommand or concept.");
  
  static struct startup_info git_startup_info;
  static int use_pager = -1;
 -static char orig_cwd[PATH_MAX];
 +static char *orig_cwd;
  static const char *env_names[] = {
        GIT_DIR_ENVIRONMENT,
        GIT_WORK_TREE_ENVIRONMENT,
@@@ -36,7 -36,8 +36,7 @@@ static void save_env(void
        if (saved_environment)
                return;
        saved_environment = 1;
 -      if (!getcwd(orig_cwd, sizeof(orig_cwd)))
 -              die_errno("cannot getcwd");
 +      orig_cwd = xgetcwd();
        for (i = 0; i < ARRAY_SIZE(env_names); i++) {
                orig_env[i] = getenv(env_names[i]);
                if (orig_env[i])
@@@ -47,9 -48,8 +47,9 @@@
  static void restore_env(void)
  {
        int i;
 -      if (*orig_cwd && chdir(orig_cwd))
 +      if (orig_cwd && chdir(orig_cwd))
                die_errno("could not move to %s", orig_cwd);
 +      free(orig_cwd);
        for (i = 0; i < ARRAY_SIZE(env_names); i++) {
                if (orig_env[i])
                        setenv(env_names[i], orig_env[i], 1);
@@@ -161,10 -161,9 +161,10 @@@ static int handle_options(const char **
                        if (envchanged)
                                *envchanged = 1;
                } else if (!strcmp(cmd, "--bare")) {
 -                      static char git_dir[PATH_MAX+1];
 +                      char *cwd = xgetcwd();
                        is_bare_repository_cfg = 1;
 -                      setenv(GIT_DIR_ENVIRONMENT, getcwd(git_dir, sizeof(git_dir)), 0);
 +                      setenv(GIT_DIR_ENVIRONMENT, cwd, 0);
 +                      free(cwd);
                        setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);
                        if (envchanged)
                                *envchanged = 1;
@@@ -282,7 -281,8 +282,7 @@@ static int handle_alias(int *argcp, con
                                  "trace: alias expansion: %s =>",
                                  alias_command);
  
 -              new_argv = xrealloc(new_argv, sizeof(char *) *
 -                                  (count + *argcp));
 +              REALLOC_ARRAY(new_argv, count + *argcp);
                /* insert after command name */
                memcpy(new_argv + count, *argv + 1, sizeof(char *) * *argcp);
  
@@@ -592,6 -592,26 +592,26 @@@ static int run_argv(int *argcp, const c
        return done_alias;
  }
  
+ /*
+  * Many parts of Git have subprograms communicate via pipe, expect the
+  * upstream of a pipe to die with SIGPIPE when the downstream of a
+  * pipe does not need to read all that is written.  Some third-party
+  * programs that ignore or block SIGPIPE for their own reason forget
+  * to restore SIGPIPE handling to the default before spawning Git and
+  * break this carefully orchestrated machinery.
+  *
+  * Restore the way SIGPIPE is handled to default, which is what we
+  * expect.
+  */
+ static void restore_sigpipe_to_default(void)
+ {
+       sigset_t unblock;
+ 
+       sigemptyset(&unblock);
+       sigaddset(&unblock, SIGPIPE);
+       sigprocmask(SIG_UNBLOCK, &unblock, NULL);
+       signal(SIGPIPE, SIG_DFL);
+ }
  
  int main(int argc, char **av)
  {
@@@ -611,6 -631,8 +631,8 @@@
         */
        sanitize_stdfds();
  
+       restore_sigpipe_to_default();
+ 
        git_setup_gettext();
  
        trace_command_performance(argv);