Merge branch 'rj/pager-die-upon-exec-failure'

When GIT_PAGER failed to spawn, depending on the code path taken,
we failed immediately (correct) or just spew the payload to the
standard output (incorrect).  The code now always fail immediately
when GIT_PAGER fails.

* rj/pager-die-upon-exec-failure:
  pager: die when paging to non-existing command

pager.c

@@ -137,7 +137,7 @@ void setup_pager(void)
 	pager_process.in = -1;
 	strvec_push(&pager_process.env, "GIT_PAGER_IN_USE");
 	if (start_command(&pager_process))
-		return;
+		die("unable to execute pager '%s'", pager);
 
 	/* original process continues, but writes to the pipe */
 	dup2(pager_process.in, 1);

t/t7006-pager.sh

@@ -725,18 +725,11 @@ test_expect_success TTY 'git discards pager non-zero exit without SIGPIPE' '
 	test_path_is_file pager-used
 '
 
-test_expect_success TTY 'git skips paging nonexisting command' '
-	test_when_finished "rm trace.normal" &&
+test_expect_success TTY 'git errors when asked to execute nonexisting pager' '
+	test_when_finished "rm -f err" &&
 	test_config core.pager "does-not-exist" &&
-	GIT_TRACE2="$(pwd)/trace.normal" &&
-	export GIT_TRACE2 &&
-	test_when_finished "unset GIT_TRACE2" &&
-
-	test_terminal git log &&
-
-	grep child_exit trace.normal >child-exits &&
-	test_line_count = 1 child-exits &&
-	grep " code:-1 " child-exits
+	test_must_fail test_terminal git log 2>err &&
+	test_grep "unable to execute pager" err
 '
 
 test_expect_success TTY 'git returns SIGPIPE on propagated signals from pager' '
@@ -762,7 +755,7 @@ test_expect_success TTY 'git returns SIGPIPE on propagated signals from pager' '
 
 test_expect_success TTY 'non-existent pager doesnt cause crash' '
 	test_config pager.show invalid-pager &&
-	test_terminal git show
+	test_must_fail test_terminal git show
 '
 
 test_done