[PATCH v2 2/5] pager: do not close fd 2 unnecessarily

["Rubén Justo" <rjusto@gmail.com>]

We send errors to the pager since 61b80509e3 (sending errors to stdout
under $PAGER, 2008-02-16).

In a8335024c2 (pager: do not dup2 stderr if it is already redirected,
2008-12-15) an exception was introduced to avoid redirecting stderr if
it is not connected to a terminal.

In such exceptional cases, the close(STDERR_FILENO) we're doing in
close_pager_fds, is unnecessary.

Furthermore, in a subsequent commit we're going to introduce changes
that might call close_pager_fds multiple times.  With this in mind,
unconditionally closing stderr will become undesirable.

Let's close(STDERR_FILENO) only when necessary, and pave the way for the
comming changes.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---
 pager.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/pager.c b/pager.c
index b8822a9381..3ef6798f7e 100644
--- a/pager.c
+++ b/pager.c
@@ -14,6 +14,7 @@ int pager_use_color = 1;
 
 static struct child_process pager_process;
 static const char *pager_program;
+static int old_fd2 = -1;
 
 /* Is the value coming back from term_columns() just a guess? */
 static int term_columns_guessed;
@@ -23,7 +24,8 @@ static void close_pager_fds(void)
 {
 	/* signal EOF to pager */
 	close(1);
-	close(2);
+	if (old_fd2 != -1)
+		close(2);
 }
 
 static void wait_for_pager_atexit(void)
@@ -141,8 +143,10 @@ void setup_pager(void)
 
 	/* original process continues, but writes to the pipe */
 	dup2(pager_process.in, 1);
-	if (isatty(2))
+	if (isatty(2)) {
+		old_fd2 = 1;
 		dup2(pager_process.in, 2);
+	}
 	close(pager_process.in);
 
 	/* this makes sure that the parent terminates after the pager */
-- 
2.45.1.221.gd3c11dbb1d