Merge branch 'jk/unify-exit-code-by-receiving-signal' into maint

* jk/unify-exit-code-by-receiving-signal:
  run-command: encode signal death as a positive integer

Documentation/technical/api-run-command.txt

@@ -55,10 +55,8 @@ The functions above do the following:
   non-zero.
 
 . If the program terminated due to a signal, then the return value is the
-  signal number - 128, ie. it is negative and so indicates an unusual
-  condition; a diagnostic is printed. This return value can be passed to
-  exit(2), which will report the same code to the parent process that a
-  POSIX shell's $? would report for a program that died from the signal.
+  signal number + 128, ie. the same value that a POSIX shell's $? would
+  report.  A diagnostic is printed.
 
 
 `start_async`::

editor.c

@@ -51,7 +51,7 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
 		sigchain_push(SIGINT, SIG_IGN);
 		sigchain_push(SIGQUIT, SIG_IGN);
 		ret = finish_command(&p);
-		sig = ret + 128;
+		sig = ret - 128;
 		sigchain_pop(SIGINT);
 		sigchain_pop(SIGQUIT);
 		if (sig == SIGINT || sig == SIGQUIT)

run-command.c

@@ -249,7 +249,7 @@ static int wait_or_whine(pid_t pid, const char *argv0)
 		 * mimics the exit code that a POSIX shell would report for
 		 * a program that died from this signal.
 		 */
-		code -= 128;
+		code += 128;
 	} else if (WIFEXITED(status)) {
 		code = WEXITSTATUS(status);
 		/*

t/test-terminal.perl

@@ -31,7 +31,7 @@ sub finish_child {
 	} elsif ($? & 127) {
 		my $code = $? & 127;
 		warn "died of signal $code";
-		return $code - 128;
+		return $code + 128;
 	} else {
 		return $? >> 8;
 	}