From 4babb839aaa18b14a5ec9e8994678d75bc120920 Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 12 Sep 2016 20:23:44 -0700
Subject: [PATCH] pager: stop loading git_default_config()

In git_pager(), we really only care about getting the value
of core.pager. But to do so, we use the git_default_config()
callback, which loads many other values. Ordinarily it
isn't a big deal to load this config an extra time, as it
simply overwrites the values from the previous run. But it's
a bad idea here, for two reasons:

  1. The pager setup may be called very early in the
     program, before we have found the git repository. As a
     result, we may fail to read the correct repo-level
     config file.  This is a problem for core.pager, too,
     but we should at least try to minimize the pollution to
     other configured values.

  2. Because we call setup_pager() from git.c, basically
     every builtin command _may_ end up reading this config
     and getting an implicit git_default_config() setup.

     Which doesn't sound like a terrible thing, except that
     we don't do it consistently; it triggers only when
     stdout is a tty. So if a command forgets to load the
     default config itself (but depends on it anyway), it
     may appear to work, and then mysteriously fail when the
     pager is not in use.

We can improve this by loading _just_ the core.pager config
from git_pager().

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 config.c | 3 ---
 pager.c  | 9 ++++++++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/config.c b/config.c
index 6dbc8a409e7..1d2331aa085 100644
--- a/config.c
+++ b/config.c
@@ -836,9 +836,6 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
-	if (!strcmp(var, "core.pager"))
-		return git_config_string(&pager_program, var, value);
-
 	if (!strcmp(var, "core.editor"))
 		return git_config_string(&editor_program, var, value);
 
diff --git a/pager.c b/pager.c
index 70159b8858c..fc210f951d5 100644
--- a/pager.c
+++ b/pager.c
@@ -35,6 +35,13 @@ static void wait_for_pager_signal(int signo)
 	raise(signo);
 }
 
+static int core_pager_config(const char *var, const char *value, void *data)
+{
+	if (!strcmp(var, "core.pager"))
+		return git_config_string(&pager_program, var, value);
+	return 0;
+}
+
 const char *git_pager(int stdout_is_tty)
 {
 	const char *pager;
@@ -45,7 +52,7 @@ const char *git_pager(int stdout_is_tty)
 	pager = getenv("GIT_PAGER");
 	if (!pager) {
 		if (!pager_program)
-			git_config(git_default_config, NULL);
+			git_config(core_pager_config, NULL);
 		pager = pager_program;
 	}
 	if (!pager)