b4: Try to download thread from piem-inboxes URL

If a call to piem-b4-am-from-mid fails to generate the thread for a
message ID via piem-mid-to-thread-functions, b4 is called without a
local mbox.  In this case, b4 tries to download the thread from the
URL specified by b4.midmask in the caller's Git configuration.

That works, but it's inconvenient because the user needs to configure
the URL in two places.  If the current buffer is associated with an
inbox in piem-inboxes, try to download the thread from its :url before
falling back to b4's midmask.

Message-Id: <20200817013343.15615-6-kyle@kyleam.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/piem.el b/piem.el
index 029b647..3669cfe 100644
--- a/piem.el
+++ b/piem.el
@@ -390,6 +390,21 @@ buffer."
   (delete-region (point) (point-max))
   (goto-char (point-min)))
 
+(defun piem--decompress-callback (status)
+  (if (plist-get status :error)
+      (kill-buffer (current-buffer))
+    (piem--url-remove-header)
+    (piem--url-decompress)))
+
+(defun piem-download-and-decompress (url)
+  "Retrieve gzipped content at URL and decompress it.
+A buffer with the decompressed content is returned.  A live
+buffer indicates that the request did not result in an error."
+  (unless (piem-check-gunzip)
+    (user-error "gunzip executable not found"))
+  (let ((url-asynchronous nil))
+    (url-retrieve url #'piem--decompress-callback)))
+
 (defun piem--write-mbox-to-maildir ()
   (let ((n-messages 0))
     (while (and (not (eobp))