[PATCH v2 2/2] pager: make wait_for_pager a no-op for "cat"

["Rubén Justo" <rjusto@gmail.com>]

If we find that the configured pager is an empty string [*1*] or simply
"cat" [*2*], then we return from `setup_pager()` silently without doing
anything, allowing the output to go directly to the normal stdout.

If `setup_pager()` avoids forking a pager, then when the client calls
the corresponding `wait_for_pager()`, we might fail trying to terminate
a process that wasn't started.

One solution to avoid this problem could be to make the caller aware
that `setup_pager()` did nothing, so it could avoid calling
`wait_for_pager()`.

However, let's avoid shifting 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 a 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>
---
 pager.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pager.c b/pager.c
index bea4345f6f..896f40fcd2 100644
--- a/pager.c
+++ b/pager.c
@@ -46,6 +46,9 @@ static void wait_for_pager_atexit(void)
 
 void wait_for_pager(void)
 {
+	if (old_fd1 == -1)
+		return;
+
 	finish_pager();
 	sigchain_pop_common();
 	unsetenv("GIT_PAGER_IN_USE");
-- 
2.45.1