Optional space and unit in `file-size-human-readable' (bug#35756)

To improve readability of strings produced by
`file-size-human-readable', add two optional arguments:

- SPACE, to provide a string (typically a space or non-breaking space)
to put between the number and unit.  For compatibility, the default is
an empty string.

- UNIT, a string to use as unit.  For compatibility, the default is
"B" in `iec' mode and the empty string otherwise.

Also fix a glitch with small numbers in `iec' mode which caused a
stray "i" in the result.

* lisp/files.el (file-size-human-readable):
Add optional SPACE and UNIT arguments and handle small numbers correctly.
(files--ask-user-about-large-file, warn-maybe-out-of-memory):
Call with `iec' and space.
* test/lisp/files-tests.el (files-test-file-size-human-readable): New test.
* lisp/url/url-http.el (url-http-simple-after-change-function)
(url-http-content-length-after-change-function): Call with `iec' and space.
* etc/NEWS (Lisp Changes): Mention the change.

1 files changed, 6 insertions, 5 deletions

diff --git a/lisp/url/url-http.el b/lisp/url/url-http.el
index 00803a103a0..527760118d4 100644
--- a/lisp/url/url-http.el
+++ b/lisp/url/url-http.el
@@ -1016,7 +1016,8 @@ should be shown to the user."
 (defun url-http-simple-after-change-function (_st _nd _length)
   ;; Function used when we do NOT know how long the document is going to be
   ;; Just _very_ simple 'downloaded %d' type of info.
-  (url-lazy-message "Reading %s..." (file-size-human-readable (buffer-size))))
+  (url-lazy-message "Reading %s..."
+                    (file-size-human-readable (buffer-size) 'iec " ")))
 
 (defun url-http-content-length-after-change-function (_st nd _length)
   "Function used when we DO know how long the document is going to be.
@@ -1029,16 +1030,16 @@ the callback to be triggered."
        (url-percentage (- nd url-http-end-of-headers)
 		       url-http-content-length)
        url-http-content-type
-       (file-size-human-readable (- nd url-http-end-of-headers))
-       (file-size-human-readable url-http-content-length)
+       (file-size-human-readable (- nd url-http-end-of-headers) 'iec " ")
+       (file-size-human-readable url-http-content-length 'iec " ")
        (url-percentage (- nd url-http-end-of-headers)
 		       url-http-content-length))
     (url-display-percentage
      "Reading... %s of %s (%d%%)"
      (url-percentage (- nd url-http-end-of-headers)
 		     url-http-content-length)
-     (file-size-human-readable (- nd url-http-end-of-headers))
-     (file-size-human-readable url-http-content-length)
+     (file-size-human-readable (- nd url-http-end-of-headers) 'iec " ")
+     (file-size-human-readable url-http-content-length 'iec " ")
      (url-percentage (- nd url-http-end-of-headers)
 		     url-http-content-length)))