git-init-db: set up the full default environment

Create .git/refs/{heads,tags} and make .git/HEAD be a symlink to
(the as yet non-existent) .git/refs/heads/master.

init-db.c

@@ -15,6 +15,41 @@ static void safe_create_dir(const char *dir)
 	}
 }
 
+static void create_default_files(const char *git_dir)
+{
+	unsigned len = strlen(git_dir);
+	static char path[PATH_MAX];
+
+	if (len > sizeof(path)-50)
+		die("insane git directory %s", git_dir);
+	memcpy(path, git_dir, len);
+
+	if (len && path[len-1] != '/')
+		path[len++] = '/';
+
+	/*
+	 * Create .git/refs/{heads,tags}
+	 */
+	strcpy(path + len, "refs");
+	safe_create_dir(path);
+	strcpy(path + len, "refs/heads");
+	safe_create_dir(path);
+	strcpy(path + len, "refs/tags");
+	safe_create_dir(path);
+
+	/*
+	 * Create the default symlink from ".git/HEAD" to the "master"
+	 * branch
+	 */
+	strcpy(path + len, "HEAD");
+	if (symlink("refs/heads/master", path) < 0) {
+		if (errno != EEXIST) {
+			perror(path);
+			exit(1);
+		}
+	}
+}
+
 /*
  * If you want to, you can share the DB area with any number of branches.
  * That has advantages: you can save space by sharing all the SHA1 objects.
@@ -23,18 +58,26 @@ static void safe_create_dir(const char *dir)
  */
 int main(int argc, char **argv)
 {
+	const char *git_dir;
 	const char *sha1_dir;
 	char *path;
 	int len, i;
 
-	sha1_dir = get_object_directory();
-	if (!gitenv(DB_ENVIRONMENT) && !gitenv(GIT_DIR_ENVIRONMENT)) {
-		/* We create leading paths only when we fall back
-		 * to local .git/objects, at least for now.
-		 */
-		safe_create_dir(DEFAULT_GIT_DIR_ENVIRONMENT);
+	/*
+	 * Set up the default .git directory contents
+	 */
+	git_dir = gitenv(GIT_DIR_ENVIRONMENT);
+	if (!git_dir) {
+		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 		fprintf(stderr, "defaulting to local storage area\n");
 	}
+	safe_create_dir(git_dir);
+	create_default_files(git_dir);
+
+	/*
+	 * And set up the object store.
+	 */
+	sha1_dir = get_object_directory();
 	len = strlen(sha1_dir);
 	path = xmalloc(len + 40);
 	memcpy(path, sha1_dir, len);