Use user-specific temp directories to prevent permission conflicts (fixes #217)

[glenneth1]

Summary

Makes temporary directories user-specific to prevent permission conflicts when multiple users run Hunchentoot tests on the same machine.

Fixes #217

Problem

When user A runs tests, /tmp/hunchentoot/ is created and owned by user A. When user B subsequently runs tests, they get permission errors trying to write to the same directory.

Change

Temp directories now include the username in the path:

;; Before
/tmp/hunchentoot/

;; After
/tmp/hunchentoot-glenn/

Uses portable UIOP:GETENV to read USER/USERNAME environment variables, with an SBCL-specific sb-posix:getuid fallback.

• specials.lisp: Added user-tmp-directory function, used for *tmp-directory*
• test/test-handlers.lisp: Added user-tmp-test-directory function, used for *tmp-test-directory*

Testing

All existing tests pass on SBCL/Linux.

[stassats]

It would be better to have atomically created randomly named temporary directories.
cl-fad seems to only have CL-FAD:OPEN-TEMPORARY, maybe it should have something for directories too.

[glenneth1]

Thanks @stassats, great suggestion. I've updated the PR to use atomically created, randomly named temporary directories.

What changed

Instead of a predictable user-specific path, *tmp-directory* is now set via a new make-tmp-directory function that creates a unique directory at load time:

SBCL (POSIX): Uses sb-posix:mkdtemp with the template /tmp/hunchentoot-XXXXXX, which atomically creates a directory with a random suffix — e.g. /tmp/hunchentoot-sZYYDd/.

CCL (POSIX): Calls mkdtemp via FFI.

Portable fallback (other implementations / Windows): Generates a random base-36 name, checks it doesn't exist, and creates it. Retries up to 100 times.

specials.lisp

(defun make-tmp-directory ()
  "Creates and returns a unique temporary directory for Hunchentoot.
On POSIX systems, uses mkdtemp for atomic creation.  On Windows,
generates a random name and creates the directory."
  #+(and :sbcl (not (or :win32 :mswindows)))
  (let ((template (format nil "/tmp/hunchentoot-XXXXXX")))
    (let ((path (sb-posix:mkdtemp template)))
      (format nil "~A/" path)))
  ...)

(defvar *tmp-directory* (make-tmp-directory)
  "Directory for temporary files created by MAKE-TMP-FILE-NAME.")

test/test-handlers.lisp

The test temp directory is now simply derived from *tmp-directory*, which is already unique per instance:

(defvar *tmp-test-directory*
    (pathname (format nil "~Atest/" *tmp-directory*)))

I agree that cl-fad having a make-temporary-directory would be the ideal long-term solution. This approach should work well in the meantime.

All existing tests pass on SBCL/Linux.