Allow multiple "git_path()" uses

[Linus Torvalds <torvalds@osdl.org>]

This allows you to maintain a few filesystem pathnames concurrently, by 
simply replacing the single static "pathname" buffer with a LRU of four 
buffers.

We did exactly the same thing with sha1_to_hex(), for pretty much exactly 
the same reason. Sometimes you want to use two pathnames, and while it's 
easy enough to xstrdup() them, why not just do the LU buffer thing.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

[ This actually came up when I was playing with git_path("refs-packed") 
  when following refs, so while it doesn't hit us right now, it's for some 
  future work.. ]

diff --git a/path.c b/path.c
index db8905f..bb89fb0 100644
--- a/path.c
+++ b/path.c
@@ -13,9 +13,15 @@
 #include "cache.h"
 #include <pwd.h>
 
-static char pathname[PATH_MAX];
 static char bad_path[] = "/bad-path/";
 
+static char *get_pathname(void)
+{
+	static char pathname_array[4][PATH_MAX];
+	static int index;
+	return pathname_array[3 & ++index];
+}
+
 static char *cleanup_path(char *path)
 {
 	/* Clean it up */
@@ -31,6 +37,7 @@ char *mkpath(const char *fmt, ...)
 {
 	va_list args;
 	unsigned len;
+	char *pathname = get_pathname();
 
 	va_start(args, fmt);
 	len = vsnprintf(pathname, PATH_MAX, fmt, args);
@@ -43,6 +50,7 @@ char *mkpath(const char *fmt, ...)
 char *git_path(const char *fmt, ...)
 {
 	const char *git_dir = get_git_dir();
+	char *pathname = get_pathname();
 	va_list args;
 	unsigned len;