substitute-binary: Pass `filtered-port' an unbuffered port.

This fixes a bug whereby `read-response' would read more than just the
response, with the extra data going into the port's buffer; the
"bzip2 -dc" process spawned by `filtered-port' would not see the those
buffered data, which are definitely lost, and would bail out with
"bzip2: (stdin) is not a bzip2 file."

* guix/utils.scm (filtered-port): Document that INPUT must be
  unbuffered.
* guix/web.scm (http-fetch): Add `buffered?' parameter.  Call
  `open-socket-for-uri' explicitly, and call `setvbuf' when BUFFERED? is
  false.  Pass the port to `http-get'.  Close it upon 301/302.
* guix/scripts/substitute-binary.scm (fetch): Add `buffered?'
  parameter.  Pass it to `http-fetch'; honor it for `file' URIs.
  (guix-substitute-binary): Call `fetch' with #:buffered? #f for port RAW.
* tests/utils.scm ("filtered-port, file"): Open FILE as unbuffered.

1 files changed, 2 insertions, 1 deletions

diff --git a/guix/utils.scm b/guix/utils.scm
index c2d2808f76..25a392e6a8 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -163,7 +163,8 @@ evaluate to a simple datum."
 (define (filtered-port command input)
   "Return an input port where data drained from INPUT is filtered through
 COMMAND (a list).  In addition, return a list of PIDs that the caller must
-wait."
+wait.  When INPUT is a file port, it must be unbuffered; otherwise, any
+buffered data is lost."
   (let loop ((input input)
              (pids '()))
     (if (file-port? input)