Add "mkpath()" helper function

I'm bored with doing it by hand all the time.

Makefile

@@ -56,7 +56,7 @@ install: $(PROG) $(SCRIPTS)
 	$(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
 
 LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
-	 tag.o date.o index.o diff-delta.o patch-delta.o entry.o \
+	 tag.o date.o index.o diff-delta.o patch-delta.o entry.o path.o \
 	 epoch.o refs.o csum-file.o pack-check.o pkt-line.o connect.o
 LIB_FILE=libgit.a
 LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h epoch.h csum-file.h \

cache.h

@@ -158,6 +158,7 @@ extern void rollback_index_file(struct cache_file *);
 #define TYPE_CHANGED    0x0040
 
 /* Return a statically allocated filename matching the sha1 signature */
+extern char *mkpath(const char *fmt, ...);
 extern char *git_path(const char *fmt, ...);
 extern char *sha1_file_name(const unsigned char *sha1);
 

path.c

+/*
+ * I'm tired of doing "vsnprintf()" etc just to open a
+ * file, so here's a "return static buffer with printf"
+ * interface for paths.
+ *
+ * It's obviously not thread-safe. Sue me. But it's quite
+ * useful for doing things like
+ *
+ *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
+ *
+ * which is what it's designed for.
+ */
+#include "cache.h"
+
+static char pathname[PATH_MAX];
+static char bad_path[] = "/bad-path/";
+
+static char *cleanup_path(char *path)
+{
+	/* Clean it up */
+	if (!memcmp(path, "./", 2)) {
+		path += 2;
+		while (*path == '/')
+			path++;
+	}
+	return path;
+}
+
+char *mkpath(const char *fmt, ...)
+{
+	va_list args;
+	unsigned len;
+
+	va_start(args, fmt);
+	len = vsnprintf(pathname, PATH_MAX, fmt, args);
+	va_end(args);
+	if (len >= PATH_MAX)
+		return bad_path;
+	return cleanup_path(pathname);
+}
+
+char *git_path(const char *fmt, ...)
+{
+	const char *git_dir = gitenv(GIT_DIR_ENVIRONMENT) ? : DEFAULT_GIT_DIR_ENVIRONMENT;
+	va_list args;
+	unsigned len;
+
+	len = strlen(git_dir);
+	if (len > PATH_MAX-100)
+		return bad_path;
+	memcpy(pathname, git_dir, len);
+	if (len && git_dir[len-1] != '/')
+		pathname[len++] = '/';
+	va_start(args, fmt);
+	len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
+	va_end(args);
+	if (len >= PATH_MAX)
+		return bad_path;
+	return cleanup_path(pathname);
+}

sha1_file.c

@@ -102,34 +102,6 @@ char *get_index_file(void)
 	return git_index_file;
 }
 
-char *git_path(const char *fmt, ...)
-{
-	static char pathname[PATH_MAX], *ret;
-	va_list args;
-	int len;
-
-	if (!git_dir)
-		setup_git_env();
-	len = strlen(git_dir);
-	if (len > PATH_MAX-100)
-		return "pad-path";
-	memcpy(pathname, git_dir, len);
-	if (len && git_dir[len-1] != '/')
-		pathname[len++] = '/';
-	va_start(args, fmt);
-	vsnprintf(pathname + len, sizeof(pathname) - len, fmt, args);
-	va_end(args);
-	ret = pathname;
-
-	/* Clean it up */
-	if (!memcmp(pathname, "./", 2)) {
-		ret += 2;
-		while (*ret == '/')
-			ret++;
-	}
-	return ret;
-}
-
 int safe_create_leading_directories(char *path)
 {
 	char *pos = path;