Merge from origin/emacs-26

a5da653 * src/editfns.c (Fnarrow_to_region): Doc fix.  (Bug#35163)
646d33d Fix doc strings of 'vc-version-diff' and 'vc-version-ediff'
a30a6c3 Improve documentation of set-window-start
92ce2dd Improve documentation of window parameters
6dc42c5 Improve commentary in frame.el
a8cffcf Fix typo in a doc string
9e79f19 (emacs-26) ; * src/fontset.c (set-fontset-font): Use uppercas...

# Conflicts:
#	lisp/vc/vc.el

3 files changed, 23 insertions, 4 deletions

diff --git a/lisp/autorevert.el b/lisp/autorevert.el
index e6dfafca2a5..4fb865e8adb 100644
--- a/lisp/autorevert.el
+++ b/lisp/autorevert.el
@@ -465,7 +465,7 @@ If `global-auto-revert-non-file-buffers' is non-nil, this mode
 may also revert some non-file buffers, as described in the
 documentation of that variable.  It ignores buffers with modes
 matching `global-auto-revert-ignore-modes', and buffers with a
-non-nil vale of `global-auto-revert-ignore-buffer'.
+non-nil value of `global-auto-revert-ignore-buffer'.
 
 When a buffer is reverted, a message is generated.  This can be
 suppressed by setting `auto-revert-verbose' to nil.
diff --git a/lisp/frame.el b/lisp/frame.el
index b39891cd142..b5c936a51eb 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -1855,6 +1855,14 @@ for FRAME."
 
 ;;;; Frame/display capabilities.
 
+;; These functions should make the features they test explicit in
+;; their names, so that when capabilities or the corresponding Emacs
+;; features change, it will be easy to find all the tests for such
+;; capabilities by a simple text search.  See more about the history
+;; and the intent of these functions in
+;; http://lists.gnu.org/archive/html/bug-gnu-emacs/2019-04/msg00004.html
+;; or in https://debbugs.gnu.org/cgi/bugreport.cgi?bug=35058#17.
+
 (declare-function msdos-mouse-p "dosfns.c")
 
 (defun display-mouse-p (&optional display)
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index e6f30c9f804..b992a8ebe09 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1806,7 +1806,12 @@ Return t if the buffer had changes, nil otherwise."
 
 ;;;###autoload
 (defun vc-version-diff (_files rev1 rev2)
-  "Report diffs between REV1 and REV2 revisions of the fileset."
+  "Report diffs between revisions REV1 and REV2 in the repository history.
+This compares two revisions of the current fileset.
+If REV1 is nil, it defaults to the current revision, i.e. revision
+of the last commit.
+If REV2 is nil, it defaults to the work tree, i.e. the current
+state of each file in the fileset."
   (interactive (vc-diff-build-argument-list-internal))
   ;; All that was just so we could do argument completion!
   (when (and (not rev1) rev2)
@@ -1891,8 +1896,14 @@ The merge base is a common ancestor between REV1 and REV2 revisions."
 
 ;;;###autoload
 (defun vc-version-ediff (files rev1 rev2)
-  "Show differences between revisions of the fileset in the
-repository history using ediff."
+  "Show differences between REV1 and REV2 of FILES using ediff.
+This compares two revisions of the files in FILES.  Currently,
+only a single file's revisions can be compared, i.e. FILES can
+specify only one file name.
+If REV1 is nil, it defaults to the current revision, i.e. revision
+of the last commit.
+If REV2 is nil, it defaults to the work tree, i.e. the current
+state of each file in FILES."
   (interactive (vc-diff-build-argument-list-internal))
   ;; All that was just so we could do argument completion!
   (when (and (not rev1) rev2)