Support GIT_PAGER_IN_USE environment variable

When deciding whether or not to turn on automatic color
support, git_config_colorbool checks whether stdout is a
tty. However, because we run a pager, if stdout is not a
tty, we must check whether it is because we started the
pager. This used to be done by checking the pager_in_use
variable.

This variable was set only when the git program being run
started the pager; there was no way for an external program
running git indicate that it had already started a pager.
This patch allows a program to set GIT_PAGER_IN_USE to a
true value to indicate that even though stdout is not a tty,
it is because a pager is being used.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/pager.c b/pager.c
index fb7a1a625a..0376953cb1 100644
--- a/pager.c
+++ b/pager.c
@@ -5,6 +5,8 @@
  * something different on Windows, for example.
  */
 
+static int spawned_pager;
+
 static void run_pager(const char *pager)
 {
 	/*
@@ -41,7 +43,7 @@ void setup_pager(void)
 	else if (!*pager || !strcmp(pager, "cat"))
 		return;
 
-	pager_in_use = 1; /* means we are emitting to terminal */
+	spawned_pager = 1; /* means we are emitting to terminal */
 
 	if (pipe(fd) < 0)
 		return;
@@ -70,3 +72,14 @@ void setup_pager(void)
 	die("unable to execute pager '%s'", pager);
 	exit(255);
 }
+
+int pager_in_use(void)
+{
+	const char *env;
+
+	if (spawned_pager)
+		return 1;
+
+	env = getenv("GIT_PAGER_IN_USE");
+	return env ? git_config_bool("GIT_PAGER_IN_USE", env) : 0;
+}