status: Relay "updating substitutes" messages.

Until now, those messages would be accumulated and displayed all at
once, when a '\n' was finally emitted by 'guix substitute'.  In the
meantime, clients would remain silent.

* guix/status.scm (bytevector-index): Change 'number' parameter to
'numbers' and adjust accordingly.
(build-event-output-port): Pass both #\newline and #\return to
'bytevector-index'.
* tests/status.scm ("build-output-port, daemon messages with LF"): New
test.

guix/status.scm

@@ -667,13 +667,14 @@ case where BV does not contain only valid UTF-8."
           (close-port port)
           str)))))
 
-(define (bytevector-index bv number offset count)
-  "Search for NUMBER in BV starting from OFFSET and reading up to COUNT bytes;
-return the offset where NUMBER first occurs or #f if it could not be found."
+(define (bytevector-index bv numbers offset count)
+  "Search for NUMBERS in BV starting from OFFSET and reading up to COUNT bytes;
+return the offset where one of NUMBERS first occurs or #f if they could not be
+found."
   (let loop ((offset offset)
              (count count))
     (cond ((zero? count) #f)
-          ((= (bytevector-u8-ref bv offset) number) offset)
+          ((memv (bytevector-u8-ref bv offset) numbers) offset)
           (else (loop (+ 1 offset) (- count 1))))))
 
 (define (split-lines str)
@@ -774,7 +775,12 @@ The second return value is a thunk to retrieve the current state."
             (set! %build-output '())
             (set! %build-output-pid #f))
           keep)
-        (match (bytevector-index bv (char->integer #\newline)
+
+        ;; Search for both '\n' and '\r'; the latter is appears in progress
+        ;; messages sent by 'guix substitute' through the daemon.
+        (match (bytevector-index bv
+                                 (list (char->integer #\newline)
+                                       (char->integer #\return))
                                  offset count)
           ((? integer? cr)
            (let* ((tail (maybe-utf8->string

tests/status.scm

@@ -124,6 +124,20 @@
     (force-output port)
     (get-status)))
 
+(test-equal "build-output-port, daemon messages with LF"
+  '((build-log #f "updating substitutes... 0%\r")
+    (build-log #f "updating substitutes... 50%\r")
+    (build-log #f "updating substitutes... 100%\r"))
+  (let ((port get-status (build-event-output-port cons '())))
+    (for-each (lambda (suffix)
+                (let ((bv (string->utf8
+                           (string-append "updating substitutes... "
+                                          suffix "\r"))))
+                  (put-bytevector port bv)
+                  (force-output port)))
+              '("0%" "50%" "100%"))
+    (reverse (get-status))))
+
 (test-equal "current-build-output-port, UTF-8 + garbage"
   ;; What about a mixture of UTF-8 + garbage?
   (let ((replacement "<22>"))