commands: allow reading attachments from a file

Currently, aerc reads a list of files to be attached to a message from
the file-picker-cmd's standard output. However, this doesn't play nice
with ranger which seems to draw itself by writing there, causing it to
be invisible in the embedded terminal.

In fact, instead of using a pipe, aerc redirects the output of the
command to a temporary file and then reads the list of files from there.
Take advantage of this approach and allow user to directly reference
this temporary file in the file-picker-cmd via the %f placeholder, which
gets expanded to the temporary file's location. If the %f placeholder
isn't present, keep the old behaviour.

So for example, now it is possible to do:

	file-picker-cmd=ranger --choosefiles=%f

in aerc.conf.

Signed-off-by: Karel Balej <balejk@matfyz.cz>
Acked-by: Robin Jarry <robin@jarry.cc>
Reviewed-by: Tim Culverhouse <tim@timculverhouse.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4ff6bbd0..8acb37e3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Remove headers from the compose window with `:header -d <name>`.
 - Add option `-r` to `:attach` to pipe the attachments in.
 - Add `msglist_gutter` and `msglist_pill` styles for message list scrollbar.
+- Add `%f` placeholder to `file-picker-cmd` which expands to a location of a
+  temporary file from which selected files will be read instead of the standard
+  output.
 
 ### Fixed