Use temporary pathname for release tarball in INSTALL

This reduces the chance of clashes when independent Lisp processes are
installing things.

Inspired by #138

Author: xach

quicklisp/dist.lisp

@@ -767,16 +767,16 @@ the given NAME."
 
 (defmethod install ((release release))
   (let ((archive (ensure-local-archive-file release))
-        (tar (qmerge "tmp/release-install.tar"))
         (output (relative-to (dist release)
                              (make-pathname :directory
                                             (list :relative "software"))))
         (tracking (install-metadata-file release)))
-    (ensure-directories-exist tar)
-    (ensure-directories-exist output)
-    (ensure-directories-exist tracking)
-    (gunzip archive tar)
-    (unpack-tarball tar :directory output)
+    (with-temporary-file (tar "release-install.tar")
+      (ensure-directories-exist tar)
+      (ensure-directories-exist output)
+      (ensure-directories-exist tracking)
+      (gunzip archive tar)
+      (unpack-tarball tar :directory output))
     (ensure-directories-exist tracking)
     (with-open-file (stream tracking
                             :direction :output

quicklisp/package.lisp

@@ -16,7 +16,8 @@
            #:file-size
            #:safely-read
            #:safely-read-file
-           #:make-versions-url))
+           #:make-versions-url
+           #:with-temporary-file))
 
 (defpackage #:ql-setup
   (:documentation

quicklisp/utils.lisp

@@ -122,3 +122,24 @@ http://foo/bar-versions.txt."
                    (subseq url 0 suffix-pos)
                    "-versions"
                    extension))))
+
+(defun call-with-temporary-file (fun template-pathname)
+  (assert (null (pathname-directory template-pathname)))
+  (let* ((relative-file (merge-pathnames template-pathname
+                                        #p"tmp/"))
+         (absolute-file (ql-setup:qmerge relative-file))
+         (randomized-file (make-pathname :name (format nil "~A-~36,5,'0R"
+                                                       (pathname-name template-pathname)
+                                                       (random #xFFFFFF))
+                                         :defaults absolute-file)))
+    (unwind-protect
+        (funcall fun randomized-file)
+      (delete-file-if-exists randomized-file))))
+
+;;; TODO: Use this where (qmerge "tmp/...") is used, when possible
+(defmacro with-temporary-file ((var template) &body body)
+  "Evaluate BODY with VAR bound to a temporary pathname created by
+adding random data to the pathname-name of TEMPLATE, which should be a
+pathname without a directory component. After evaluation, the
+temporary pathname is deleted if it exists."
+  `(call-with-temporary-file (lambda (,var) ,@body) ,template))