Improve documentation of VC commands, including in Dired

* doc/emacs/dired.texi (Operating on Files):
* doc/emacs/maintaining.texi (VC Change Log, VC Directory Mode)
(Version Control, Basic VC Editing): Document VC command
invocation from Dired buffers.  Improve documentation of vc-log
commands.

* lisp/dired-aux.el (dired-vc-next-action):
* lisp/vc/vc.el (vc-print-log, vc-log-search, vc-log-mergebase)
(vc-log-view-type, vc-print-root-log, vc-next-action): Doc fixes.

doc/emacs/dired.texi

@@ -715,6 +715,10 @@ Otherwise, the command operates on the current file only.
 Certain other Dired commands, such as @kbd{!} and the @samp{%}
 commands, use the same conventions to decide which files to work on.
 
+  In addition to Dired commands described here, you can also invoke
+Version Control (VC) commands on one or more files shown in a Dired
+buffer.  @xref{Version Control}.
+
 @vindex dired-dwim-target
 @cindex two directories (in Dired)
   Commands which ask for a destination directory, such as those which

doc/emacs/maintaining.texi

@@ -94,6 +94,20 @@ is useful when you perform version control commands outside Emacs
 different version control system, or remove it from version control
 entirely.
 
+@cindex VC commands, in Dired buffers
+@cindex filesets, VC, in Dired buffers
+  VC is also enabled automatically in Dired buffers (@pxref{Dired})
+showing directories whose files are controlled by a VCS@.  All VC
+commands described in this section can be invoked from any Dired
+buffer showing a directory with VC-controlled files; any files that
+are marked in a Dired buffer (@pxref{Marks vs Flags}) are considered
+to belong to the current fileset, and VC commands operate on the files
+in this fileset.  This allows you to construct VC filesets including
+any files you want, regardless of their VC state.  (If no files are
+marked when a VC command is invoked from a Dired buffer, the file
+shown on the current line in the buffer is considered the only file in
+the fileset.)
+
 @menu
 * Introduction to VC::  How version control works in general.
 * VC Mode Line::        How the mode line shows version control status.
@@ -471,9 +485,10 @@ collection of one or more files that a VC operation acts on.  When you
 type VC commands in a buffer visiting a version-controlled file, the
 VC fileset is simply that one file.  When you type them in a VC
 Directory buffer, and some files in it are marked, the VC fileset
-consists of the marked files (@pxref{VC Directory Mode}).  The VC
+consists of the marked files (@pxref{VC Directory Mode}).  Likewise,
-fileset also consists of the marked files in a Dired buffer
+when you invoke a VC command from a Dired buffer, the VC fileset
-(@pxref{Dired}).
+consists of the marked files (@pxref{Marks vs Flags}), defaulting to
+the file shown on the current line if no files are marked.
 
   On modern changeset-based version control systems (@pxref{VCS
 Changesets}), VC commands handle multi-file VC filesets as a group.
@@ -497,7 +512,9 @@ action on the current VC fileset: either registering it with a version
 control system, or committing it, or unlocking it, or merging changes
 into it.  The precise actions are described in detail in the following
 subsections.  You can use @kbd{C-x v v} either in a file-visiting
-buffer, in a Dired buffer, or in a VC Directory buffer.
+buffer, in a Dired buffer, or in a VC Directory buffer; in the latter
+two cases the command operates on the fileset consisting of the marked
+files.
 
   Note that VC filesets are distinct from the named filesets used
 for viewing and visiting files in functional groups
@@ -1002,16 +1019,25 @@ Search the change history for a specified pattern.
 @findex vc-print-log
   @kbd{C-x v l} (@code{vc-print-log}) displays a buffer named
 @file{*vc-change-log*}, showing the history of changes made to the
-current file, including who made the changes, the dates, and the log
+current fileset in the long form, including who made the changes, the
-entry for each change (these are the same log entries you would enter
+dates, and the log entry for each change (these are the same log
-via the @file{*vc-log*} buffer; @pxref{Log Buffer}).  Point is
+entries you would enter via the @file{*vc-log*} buffer; @pxref{Log
-centered at the revision of the file currently being visited.  With a
+Buffer}).  When invoked from a buffer visiting a file, the current
-prefix argument, the command prompts for the revision to center on,
+fileset consists of that single file, and point in the displayed
-and the maximum number of revisions to display.
+@file{*vc-change-log*} buffer is centered at the revision of that
+file.  When invoked from a VC Directory buffer (@pxref{VC Directory
+Mode}) or from a Dired buffer (@pxref{Dired}), the fileset consists of
+all the marked files, defaulting to the file shown on the current line
+in the directory buffer if no file is marked.
 
-  If you call @kbd{C-x v l} from a VC Directory buffer (@pxref{VC
+  If the fileset includes one or more directories, the resulting
-Directory Mode}) or a Dired buffer (@pxref{Dired}), it applies to the
+@file{*vc-change-log*} buffer shows a short log of changes (one line
-file listed on the current line or to all the marked files.
+for each change), if the VC backend supports that; otherwise it shows
+the log in the long form.
+
+  With a prefix argument, the command prompts for the revision to
+center on in the @file{*vc-change-log*} buffer and for the maximum
+number of revisions to display.
 
 @kindex C-x v L
 @findex vc-print-root-log
@@ -1217,6 +1243,11 @@ called PCL-CVS which is specialized for CVS@.  @xref{Top, , About
 PCL-CVS, pcl-cvs, PCL-CVS---The Emacs Front-End to CVS}.
 @end ifnottex
 
+  You can also invoke VC commands from Dired buffers (@pxref{Dired}).
+In that case, any VC command you invoke considers the marked files as
+the current fileset (@pxref{Basic VC Editing}), defaulting to the file
+on the current line if no files are marked.
+
 @menu
 * Buffer: VC Directory Buffer.      What the buffer looks like and means.
 * Commands: VC Directory Commands.  Commands to use in a VC directory buffer.

lisp/dired-aux.el

@@ -3741,12 +3741,21 @@ of the target of the link instead."
 
 ;;;###autoload
 (defun dired-vc-next-action (verbose)
-  "Do the next version control operation on marked files/directories.
+  "Do the next logical version control operation on marked files/directories.
-When only files are marked then call `vc-next-action' with the
+The VC control operation will operate on a fileset which includes
-same value of the VERBOSE argument.
+the marked files/directories.  If no files/directories are marked, the
-When also directories are marked then call `vc-dir' and mark
+fileset will include the single file/directory shown on the current line.
-the same files/directories in the VC-Dir buffer that were marked
+
-in the Dired buffer."
+If only regular files are in the fileset, call `vc-next-action' with
+the same value of the VERBOSE argument (interactively, the prefix
+argument).
+
+If one or more directories are in the fileset, start `vc-dir' in the root
+directory of the repository that includes the current directory, with
+the same files/directories marked in the VC-Directory buffer that were
+marked in the original Dired buffer.  If the current directory doesn't
+belong to a VCS repository, prompt for a repository directory.  In this
+case, the VERBOSE argument is ignored."
   (interactive "P")
   (let* ((marked-files
           (dired-get-marked-files nil nil nil nil t))

lisp/vc/vc.el

@@ -1239,7 +1239,11 @@ For old-style locking-based version control systems, like RCS:
 
 When using this command to register a new file (or files), it
 will automatically deduce which VC repository to register it
-with, using the most specific one."
+with, using the most specific one.
+
+If VERBOSE is non-nil (interactively, the prefix argument),
+you can specify a VC backend or (for centralized VCS only)
+the revision ID or branch ID."
   (interactive "P")
   (let* ((vc-fileset (vc-deduce-fileset nil t 'state-model-only-files))
          (backend (car vc-fileset))
@@ -2696,7 +2700,16 @@ earlier revisions.  Show up to LIMIT entries (non-nil means unlimited)."
                               is-start-revision limit type)))))
 
 (defvar vc-log-view-type nil
-  "Set this to differentiate the different types of logs.")
+  "Set this to record the type of VC log shown in the current buffer.
+Supported values are:
+
+  `short'        -- short log form, one line for each commit
+  `long'         -- long log form, including full log message and author
+  `with-diff'    -- log including diffs
+  `log-outgoing' -- log of changes to be pushed to upstream
+  `log-incoming' -- log of changes to be brought by pulling from upstream
+  `log-search'   -- log entries matching a pattern; shown in long format
+  `mergebase'    -- log created by `vc-log-mergebase'.")
 (put 'vc-log-view-type 'permanent-local t)
 (defvar vc-sentinel-movepoint)
 
@@ -2753,13 +2766,20 @@ Each function runs in the log output buffer without args.")
 
 ;;;###autoload
 (defun vc-print-log (&optional working-revision limit)
-  "List the change log of the current fileset in a window.
+  "Show in another window the VC change history of the current fileset.
-If WORKING-REVISION is non-nil, leave point at that revision.
+If WORKING-REVISION is non-nil, it should be a revision ID; position
+point in the change history buffer at that revision.
 If LIMIT is non-nil, it should be a number specifying the maximum
 number of revisions to show; the default is `vc-log-show-limit'.
 
 When called interactively with a prefix argument, prompt for
-WORKING-REVISION and LIMIT."
+WORKING-REVISION and LIMIT.
+
+This shows a short log (one line for each commit) if the current
+fileset includes directories and the VC backend supports that;
+otherwise it shows the detailed log of each commit, which includes
+the full log message and the author.  Additional control of the
+shown log style is available via `vc-log-short-style'."
   (interactive
    (cond
     (current-prefix-arg
@@ -2784,14 +2804,14 @@ WORKING-REVISION and LIMIT."
 
 ;;;###autoload
 (defun vc-print-root-log (&optional limit revision)
-  "List the revision history for the current VC controlled tree in a window.
+  "Show in another window VC change history of the current VC controlled tree.
 If LIMIT is non-nil, it should be a number specifying the maximum
 number of revisions to show; the default is `vc-log-show-limit'.
-When called interactively with a prefix argument, prompt for LIMIT.
+When called interactively with a prefix argument, prompt for LIMIT, but
-When the prefix argument is a number, use it as LIMIT.
+if the prefix argument is a number, use it as LIMIT.
 A special case is when the prefix argument is 1: in this case
-the command asks for the ID of a revision, and shows that revision
+the command prompts for the ID of a revision, and shows that revision
-with its diffs (if the underlying VCS supports that)."
+with its diffs (if the underlying VCS backend supports that)."
   (interactive
    (cond
     ((eq current-prefix-arg 1)
@@ -2875,15 +2895,17 @@ In some version control systems REMOTE-LOCATION can be a remote branch name."
 
 ;;;###autoload
 (defun vc-log-search (pattern)
-  "Search the log of changes for PATTERN.
+  "Search the VC log of changes for PATTERN and show log of matching changes.
 
 PATTERN is usually interpreted as a regular expression.  However, its
 exact semantics is up to the backend's log search command; some can
 only match fixed strings.
 
-Display all entries that match log messages in long format.
+This command displays in long format all the changes whose log messages
-With a prefix argument, ask for a command to run that will output
+match PATTERN.
-log entries."
+
+With a prefix argument, the command asks for a shell command to run that
+will output log entries, and displays those log entries instead."
   (interactive (list (unless current-prefix-arg
                        (read-regexp "Search log with pattern: "))))
   (let ((backend (vc-deduce-backend)))
@@ -2894,8 +2916,8 @@ log entries."
 
 ;;;###autoload
 (defun vc-log-mergebase (_files rev1 rev2)
-  "Show a log of changes between the merge base of REV1 and REV2 revisions.
+  "Show a log of changes between the merge base of revisions REV1 and REV2.
-The merge base is a common ancestor between REV1 and REV2 revisions."
+The merge base is a common ancestor of revisions REV1 and REV2."
   (interactive
    (vc-diff-build-argument-list-internal
     (or (ignore-errors (vc-deduce-fileset t))