Add core.pager config variable.

This adds a configuration variable that performs the same function as,
but is overridden by, GIT_PAGER.

Signed-off-by: Brian Gernhardt <benji@silverinsanity.com>
Acked-by: Johannes E. Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -281,6 +281,10 @@ core.excludesfile::
 	of files which are not meant to be tracked.  See
 	gitlink:gitignore[5].
 
+core.pager::
+	The command that git will use to paginate output.  Can be overridden
+	with the `GIT_PAGER` environment variable.
+
 alias.*::
 	Command aliases for the gitlink:git[1] command wrapper - e.g.
 	after defining "alias.last = cat-file commit HEAD", the invocation

cache.h

@@ -546,6 +546,7 @@ extern int write_or_whine_pipe(int fd, const void *buf, size_t count, const char
 
 /* pager.c */
 extern void setup_pager(void);
+extern char *pager_program;
 extern int pager_in_use;
 extern int pager_use_color;
 

config.c

@@ -387,6 +387,11 @@ int git_default_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.pager")) {
+		pager_program = xstrdup(value);
+		return 0;
+	}
+
 	/* Add other config variables here and to Documentation/config.txt. */
 	return 0;
 }

environment.c

@@ -30,6 +30,7 @@ int core_compression_seen;
 size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
 size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
 size_t delta_base_cache_limit = 16 * 1024 * 1024;
+char *pager_program;
 int pager_in_use;
 int pager_use_color = 1;
 int auto_crlf = 0;	/* 1: both ways, -1: only when adding git objects */

pager.c

@@ -31,6 +31,8 @@ void setup_pager(void)
 
 	if (!isatty(1))
 		return;
+	if (!pager)
+		pager = pager_program;
 	if (!pager)
 		pager = getenv("PAGER");
 	if (!pager)