Add "const" qualifier to "char *pager_program".

Also use "git_config_string" to simplify "config.c" code
where "pager_program" is set.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -610,7 +610,7 @@ 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 const char *pager_program;
 extern int pager_in_use(void);
 extern int pager_use_color;
 

config.c

@@ -440,12 +440,8 @@ int git_default_config(const char *var, const char *value)
 		return 0;
 	}
 
-	if (!strcmp(var, "core.pager")) {
-		if (!value)
-			return config_error_nonbool(var);
-		pager_program = xstrdup(value);
-		return 0;
-	}
+	if (!strcmp(var, "core.pager"))
+		return git_config_string(&pager_program, var, value);
 
 	if (!strcmp(var, "core.editor")) {
 		if (!value)

environment.c

@@ -30,7 +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;
+const char *pager_program;
 int pager_use_color = 1;
 char *editor_program;
 char *excludes_file;