docs: update documentation

Update the mu-find man-page; update NEWS.org and mu4e.texi for the way
threading works.

NEWS.org

@@ -5,13 +5,13 @@
 
 *** mu
 
-    - Where available (and with suitable ~libglib~), log to the systemd journal
+    - Where available (and with suitably equiped ~libglib~), log to the ~systemd~
-      instead of a ~~/.cache/mu.log~. The ~--debug~ option to ~mu~ much
+      journal instead of ~~/.cache/mu.log~. Passing the ~--debug~ option to ~mu~
       increases the amount that is logged.
 
     - Follow symlinks in maildirs, and support moving messsages across
-      filesystems (but note that that is quite a bit slower than the
+      filesystems. Obviously, that is typically quite a bit slower than the
-      single-filesystem case)
+      single-filesystem case, but can be still be useful.
 
     - Optionally provide readline support for the ~mu~ server (when in tty-mode)
 
@@ -32,8 +32,7 @@
 
     - Modernized the querying/threading machinery; this is makes some old code a
       lot easier to understand and maintain, and even while not an explicit
-      goal, is also faster (e.g. the threading seems to be roughly twice as
+      goal, is also faster.
-      fast)
 
     - Experimental support for the Meson build system.
 
@@ -53,7 +52,7 @@
     - Honor ~truncate-string-ellipsis~ so you can now use 'fancy' ellipses for
       truncated strings with ~(setq truncate-string-ellipsis "…")~
 
-    - Add a variable ~mu4e-mu-debug~ which, when set to non-~nil~ makes the ~mu~
+    - Add a variable ~mu4e-mu-debug~ which, when set to non-~nil,~ makes the ~mu~
       server log more verbosely (to ~mu.log~ or the journal)
 
     - Better alignment in headers-buffers; this looks nicer, but is also a bit

man/mu-find.1

@@ -1,11 +1,9 @@
-.TH MU FIND 1 "19 April 2015" "User Manuals"
+.TH MU FIND 1 "12 February 2021" "User Manuals"
 
 .SH NAME
 
 mu find \- find e-mail messages in the \fBmu\fR database.
 
-mu mfind \- find e-mail messages in the \fBmu\fR database with mu4e defaults.
-
 .SH SYNOPSIS
 
 .B mu find [options] <search expression>
@@ -15,9 +13,6 @@ mu mfind \- find e-mail messages in the \fBmu\fR database with mu4e defaults.
 \fBmu find\fR is the \fBmu\fR command for searching e-mail message
 that were stored earlier using \fBmu index\fR(1).
 
-\fBmu mfind\fR is a version of \fBmu find\fR that defaults to
-\f--include-related\fR and \fB--skip-dups\fR, just like \fBmu4e\fR does.
-
 .SH SEARCHING MAIL
 
 \fBmu find\fR starts a search for messages in the database that match
@@ -226,9 +221,10 @@ Gmail-style 'conversations'. Note, finding these related messages make
 searches slower.
 
 .TP
-\fB\-t\fR, \fB\-\-threads\fR show messages in a 'threaded' format -- that is,
+\fB\-t\fR, \fB\-\-threads\fR show messages in a 'threaded' format --
-with indentation and arrows showing the conversation threads in the list of
+that is, with indentation and arrows showing the conversation threads
-matching messages.
+in the list of matching messages. When using this, sorting is
+chronological (by date), based on the newest message in a thread.
 
 Messages in the threaded list are indented based on the depth in the
 discussion, and are prefix with a kind of arrow with thread-related

mu4e/mu4e-headers.el

@@ -220,7 +220,11 @@ but also manually invoked searches."
 (defvar mu4e-headers-sort-field :date
   "Field to sort the headers by. Must be a symbol,
 one of: `:date', `:subject', `:size', `:prio', `:from', `:to.',
-`:list'")
+`:list'.
+
+Note that when threading is enabled (through
+`mu4e-headers-show-threads'), the headers are exclusively sorted
+chronologically (`:date') by the newest message in the thread.")
 
 (defvar mu4e-headers-sort-direction 'descending
   "Direction to sort by; a symbol either `descending' (sorting

mu4e/mu4e.texi

@@ -379,12 +379,24 @@ configuration before trying again:
 (add-to-list 'load-path "/usr/local/share/emacs/site-lisp/mu4e")
 @end lisp
 
+@subsection Building using the meson build system
+
+As an (experimental) alternative to the @t{autotools}-build, it is possible to use
+the Meson@footnote{@url{https://mesonbuild.com/}} build-system instead.
+
+@example
+$ git clone git://github.com/djcb/mu.git
+$ cd mu
+$ meson build && ninja -C build
+$ sudo ninja -C install
+@end example
+
 @subsection mu4e and emacs customization
 
 There is some support for using the Emacs customization system in
-@t{mu4e}, but for now, we recommend setting the values manually. Please refer
+@t{mu4e}, but for now, we recommend setting the values
-to @ref{Example configs} for a couple of examples of this; here we go
+manually. Please refer to @ref{Example configs} for a couple of
-through things step-by-step.
+examples of this; here we go through things step-by-step.
 
 @node Getting mail
 @section Getting mail
@@ -1046,17 +1058,19 @@ For more information about marking, see @ref{Marking}.
 @node Sorting and threading
 @section Sorting and threading
 
-By default, @t{mu4e} sorts messages by date, in descending order: the most
+By default, @t{mu4e} sorts messages by date, in descending order: the
-recent messages are shown at the top. In addition, the messages are
+most recent messages are shown at the top. In addition, be default
-@emph{threaded}, i.e., shown in the context of a discussion thread; this also
+@t{mu4e} shows the message @emph{threads}, i.e., the tree structure
-affects the sort order.
+representing a discussion thread; this also affects the sort order:
+the top-level messages are sorted by the date of the @emph{newest}
+message in the thread.
 
 The header field used for sorting is indicated by ``@t{V}'' or
 ``@t{^}''@footnote{or you can use little graphical triangles; see variable
 @code{mu4e-use-fancy-chars}}, indicating the sort order (descending or
 ascending, respectively).
 
-You can change the sort order by clicking the corresponding field with the
+You can change the sort order by clicking the corresponding column with the
 mouse, or with @kbd{M-x mu4e-headers-change-sorting} (@key{O}); note that not
 all fields can be used for sorting. You can toggle threading on/off using
 @kbd{M-x mu4e-headers-toggle-threading} or @key{P}. For both of these functions,
@@ -1064,6 +1078,9 @@ unless you provide a prefix argument (@key{C-u}), the current search is
 updated immediately using the new parameters. You can toggle full-search
 (@ref{Searching}) using @kbd{M-x mu4e-headers-toggle-full-search} or @key{Q}.
 
+Note that with threading enabled, the sorting is exclusively by date,
+regardless of the column clicked.
+
 If you want to change the defaults for these settings, you can use the
 variables @code{mu4e-headers-sort-field} and
 @code{mu4e-headers-show-threads}, as well as