Improve documentation of dabbrevs

* lisp/dabbrev.el (dabbrev-expand): Doc fix.  (Bug#24890)

* doc/emacs/abbrevs.texi (Dynamic Abbrevs): Mention
'dabbrev-check-all-buffers', 'dabbrev-check-other-buffers', and
'dabbrev-ignored-buffer-names' and their purpose.  (Bug#24890)

2 files changed, 15 insertions, 7 deletions

diff --git a/doc/emacs/abbrevs.texi b/doc/emacs/abbrevs.texi
index a1db34cf0ee..227fe6f7ee2 100644
--- a/doc/emacs/abbrevs.texi
+++ b/doc/emacs/abbrevs.texi
@@ -341,7 +341,7 @@ abbrev expansion happens only when you request it explicitly.
 @table @kbd
 @item M-/
 Expand the word in the buffer before point as a @dfn{dynamic abbrev},
-by searching in the buffer for words starting with that abbreviation
+by searching for words starting with that abbreviation
 (@code{dabbrev-expand}).
 
 @item C-M-/
@@ -361,14 +361,19 @@ The variable @code{dabbrev-limit}, if non-@code{nil}, specifies how far
 away in the buffer to search for an expansion.
 
 @vindex dabbrev-check-all-buffers
+@vindex dabbrev-check-other-buffers
   After scanning the current buffer, @kbd{M-/} normally searches other
-buffers, unless you have set @code{dabbrev-check-all-buffers} to
-@code{nil}.
+buffers.  The variables @code{dabbrev-check-all-buffers} and
+@code{dabbrev-check-other-buffers} can be used to determine which
+other buffers, if any, are searched.
 
+@vindex dabbrev-ignored-buffer-names
 @vindex dabbrev-ignored-buffer-regexps
-  For finer control over which buffers to scan, customize the variable
-@code{dabbrev-ignored-buffer-regexps}.  Its value is a list of regular
-expressions.  If a buffer's name matches any of these regular
+  For finer control over which buffers to scan, customize the
+variables @code{dabbrev-ignored-buffer-names} and
+@code{dabbrev-ignored-buffer-regexps}.  The value of the former is a
+list of buffer names to skip.  The value of the latter is a list of
+regular expressions; if a buffer's name matches any of these regular
 expressions, dynamic abbrev expansion skips that buffer.
 
   A negative argument to @kbd{M-/}, as in @kbd{C-u - M-/}, says to
diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index d9f36b15290..438eda3776d 100644
--- a/lisp/dabbrev.el
+++ b/lisp/dabbrev.el
@@ -433,7 +433,10 @@ Expands to the most recent, preceding word for which this is a prefix.
 If no suitable preceding word is found, words following point are
 considered.  If still no suitable word is found, then look in the
 buffers accepted by the function pointed out by variable
-`dabbrev-friend-buffer-function'.
+`dabbrev-friend-buffer-function', if `dabbrev-check-other-buffers'
+says so.  Then, if `dabbrev-check-all-buffers' is non-nil, look in
+all the other buffers, subject to constraints specified
+by `dabbrev-ignored-buffer-names' and `dabbrev-ignored-regexps'.
 
 A positive prefix argument, N, says to take the Nth backward *distinct*
 possibility.  A negative argument says search forward.