config: allow for platform-specific core.* config settings

In the Git for Windows project, we have ample precendent for config
settings that apply to Windows, and to Windows only.

Let's formalize this concept by introducing a platform_core_config()
function that can be #define'd in a platform-specific manner.

This will allow us to contain platform-specific code better, as the
corresponding variables no longer need to be exported so that they can
be defined in environment.c and be set in config.c

Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

compat/mingw.c

@@ -203,6 +203,11 @@ static int ask_yes_no_if_possible(const char *format, ...)
 	}
 }
 
+int mingw_core_config(const char *var, const char *value, void *cb)
+{
+	return 0;
+}
+
 /* Normalizes NT paths as returned by some low-level APIs. */
 static wchar_t *normalize_ntpath(wchar_t *wbuf)
 {

compat/mingw.h

@@ -11,6 +11,9 @@ typedef _sigset_t sigset_t;
 #undef _POSIX_THREAD_SAFE_FUNCTIONS
 #endif
 
+extern int mingw_core_config(const char *var, const char *value, void *cb);
+#define platform_core_config mingw_core_config
+
 /*
  * things that are not available in header files
  */

config.c

@@ -1093,7 +1093,7 @@ int git_config_color(char *dest, const char *var, const char *value)
 	return 0;
 }
 
-static int git_default_core_config(const char *var, const char *value)
+static int git_default_core_config(const char *var, const char *value, void *cb)
 {
 	/* This needs a better name */
 	if (!strcmp(var, "core.filemode")) {
@@ -1363,7 +1363,7 @@ static int git_default_core_config(const char *var, const char *value)
 	}
 
 	/* Add other config variables here and to Documentation/config.txt. */
-	return 0;
+	return platform_core_config(var, value, cb);
 }
 
 static int git_default_i18n_config(const char *var, const char *value)
@@ -1451,7 +1451,7 @@ static int git_default_mailmap_config(const char *var, const char *value)
 int git_default_config(const char *var, const char *value, void *cb)
 {
 	if (starts_with(var, "core."))
-		return git_default_core_config(var, value);
+		return git_default_core_config(var, value, cb);
 
 	if (starts_with(var, "user."))
 		return git_ident_config(var, value, cb);

git-compat-util.h

@@ -342,6 +342,14 @@ typedef uintmax_t timestamp_t;
 #define _PATH_DEFPATH "/usr/local/bin:/usr/bin:/bin"
 #endif
 
+#ifndef platform_core_config
+static inline int noop_core_config(const char *var, const char *value, void *cb)
+{
+	return 0;
+}
+#define platform_core_config noop_core_config
+#endif
+
 #ifndef has_dos_drive_prefix
 static inline int git_has_dos_drive_prefix(const char *path)
 {