Snapshot primitives globally renamed to refer to tags, documentation updated.

15 files changed, 205 insertions, 201 deletions

diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog
index e66e7f2c5bc..1d5328a606b 100644
--- a/doc/emacs/ChangeLog
+++ b/doc/emacs/ChangeLog
@@ -1,3 +1,10 @@
+2008-05-15  Eric S. Raymond  <esr@snark.thyrsus.com>
+
+	* vc2-xtra.texi, emacs.texi, files.texi: Snapshots node renamed to
+	Revision Tags and rewritten. Section now uses modern terminology
+	(tags rather than snapshots) and describes post-SCCS systems more 
+	accurately.
+
 2008-05-10  Eli Zaretskii  <eliz@gnu.org>
 
 	* msdog.texi (Windows Files): Update documentation of
diff --git a/doc/emacs/emacs.texi b/doc/emacs/emacs.texi
index 28b72eb5c13..b9d2a0993c6 100644
--- a/doc/emacs/emacs.texi
+++ b/doc/emacs/emacs.texi
@@ -119,7 +119,7 @@ and to avoid conflicts.
 Completion
 Backup Files
 Auto-Saving: Protection Against Disasters
-Snapshots
+Tags
 Text Mode
 Outline Mode
 @TeX{} Mode
@@ -462,7 +462,7 @@ Version Control
 * Secondary VC Commands:: The commands used a little less frequently.
 * Branches::            Multiple lines of development.
 * Remote Repositories:: Efficient access to remote CVS servers.
-* Snapshots::           Sets of file versions treated as a unit.
+* Revision Tags::       Symbolic names for revisions
 * Miscellaneous VC::    Various other commands and features of VC.
 * Customizing VC::      Variables that change VC's behavior.
 
diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index 9d525393004..0d6808d9e45 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -1238,7 +1238,7 @@ customizable variable @code{vc-handled-backends} to @code{nil}
 * Branches::            Multiple lines of development.
 @ifnottex
 * Remote Repositories:: Efficient access to remote CVS servers.
-* Snapshots::           Sets of file versions treated as a unit.
+* Revision Tags::       Symbolic names for revisions
 * Miscellaneous VC::    Various other commands and features of VC.
 * Customizing VC::      Variables that change VC's behavior.
 @end ifnottex
@@ -1300,8 +1300,8 @@ git, and Mercurial.
   SCCS was the first version-control system ever built, and was long ago
 superseded by later and more advanced ones; Emacs supports it only for
 backward compatibility and historical reasons.  VC compensates for
-certain features missing in SCCS (snapshots, for example) by
-implementing them itself, but some other VC features, such as multiple
+certain features missing in SCCS (tag names for releases, for example) by
+implementing them itself. Some other VC features, such as multiple
 branches, are not available with SCCS.  Since SCCS is non-free you
 should not use it; use its free replacement CSSC instead.  But you
 should use CSSC only if for some reason you cannot use a more 
@@ -1895,19 +1895,19 @@ buffer in another window.
 
   You can specify a checked-in revision by its ID; an empty input
 specifies the current contents of the work file (which may be different
-from all the checked-in revisions).  You can also specify a snapshot name
+from all the checked-in revisions).  You can also specify a tag or branch name
 @iftex
-(@pxref{Snapshots,,,emacs-xtra, Specialized Emacs Features})
+(@pxref{Tags,,,emacs-xtra, Specialized Emacs Features})
 @end iftex
 @ifnottex
-(@pxref{Snapshots})
+(@pxref{Tags})
 @end ifnottex
 instead of one or both revision ID.
 
   Note that if your version-control system is file-oriented (SCCS,
 RCS, CVS) rather than fileset-oriented (Subversion, GNU Arch, git,
 Mercurial) specifying a revision of a multiple-file fileset by
-revision ID (as opposed to a snapshot name or RSCCS/RCS tag) is
+revision ID (as opposed to a symbolic tag name) is
 unlikely to return diffs that are connected in any meaningful way.
 
   If you invoke @kbd{C-u C-x v =} or @kbd{C-u C-x v =} from a buffer
diff --git a/doc/emacs/vc-xtra.texi b/doc/emacs/vc-xtra.texi
index d08f6b29bf3..f1977d2adb6 100644
--- a/doc/emacs/vc-xtra.texi
+++ b/doc/emacs/vc-xtra.texi
@@ -14,9 +14,9 @@ the Emacs Manual}).  This chapter describes more advanced VC usage.
 
 @menu
 * VC Directory Mode::       Listing files managed by version control.
-* VC Directory Commands::   Commands to use in a VC Dired buffer.
+* VC Directory Commands:: Commands to use in a VC Dired buffer.
 * Remote Repositories::     Efficient access to remote VCS servers.
-* Snapshots::               Sets of file versions treated as a unit.
+* Revision Tags::           Symbolic names for revisions
 * Miscellaneous VC::        Various other commands and features of VC.
 * Customizing VC::          Variables that change VC's behavior.
 @end menu
diff --git a/doc/emacs/vc2-xtra.texi b/doc/emacs/vc2-xtra.texi
index c4d6eac0c46..bbb7a9980bd 100644
--- a/doc/emacs/vc2-xtra.texi
+++ b/doc/emacs/vc2-xtra.texi
@@ -204,51 +204,57 @@ and what is not.  So we suggest that you return from time to time to
 CVS-only operation, by committing your local changes back to the
 repository using @kbd{C-u C-x v v cvs @key{RET}}.
 
-@node Snapshots
-@subsection Snapshots
-@cindex snapshots and version control
+@node Revision Tags
+@subsection Revision Tags
+@cindex tags and version control
 
-  A @dfn{snapshot} is a named set of file versions (one for each
-registered file) that you can treat as a unit.  One important kind of
-snapshot is a @dfn{release}, a (theoretically) stable version of the
-system that is ready for distribution to users.
+  In a VCS with per-file revision numbers (such as SCCS, RCS, or CVS)
+@dfn{tag} is a named set of file versions (one for each registered
+file) that you can treat as a unit.  In a VCS with per-repository
+version numbers (Subversion and most later ones) a tag is simply
+a symbolic name for a revsion.
+
+   One important kind of tag is a @dfn{release}, a (theoretically)
+stable version of the system that is ready for distribution to users.
 
 @menu
-* Making Snapshots::		The snapshot facilities.
-* Snapshot Caveats::		Things to be careful of when using snapshots.
+* Making Revision Tags::		The tag facilities.
+* Revision Tag Caveats::		Things to be careful of when using tags.
 @end menu
 
-@node Making Snapshots
-@subsubsection Making and Using Snapshots
+@node Making Revision Tags
+@subsubsection Making and Using Revision Tags
 
-  There are two basic commands for snapshots; one makes a
-snapshot with a given name, the other retrieves a named snapshot.
+  There are two basic commands for tags; one makes a
+tag with a given name, the other retrieves a named tag.
 
 @table @code
 @kindex C-x v s
-@findex vc-create-snapshot
+@findex vc-create-tag
 @item C-x v s @var{name} @key{RET}
-Define the last saved versions of every registered file in or under the
-current directory as a snapshot named @var{name}
-(@code{vc-create-snapshot}).
+Define the working revision of every registered file in or under the
+current directory as a tag named @var{name}
+(@code{vc-create-tag}).
 
 @kindex C-x v r
-@findex vc-retrieve-snapshot
+@findex vc-retrieve-tag
 @item C-x v r @var{name} @key{RET}
-For all registered files at or below the current directory level, select
-whatever versions correspond to the snapshot @var{name}
-(@code{vc-retrieve-snapshot}).
+For all registered files at or below the current directory level,
+retrieve the tagged revision @var{name}. This command will 
+switch to a branch if @var{name} is a branch name and your VCS
+distinguishes branches from tags. 
+(@code{vc-retrieve-tag}).
 
 This command reports an error if any files are locked at or below the
 current directory, without changing anything; this is to avoid
 overwriting work in progress.
 @end table
 
-  A snapshot uses a very small amount of resources---just enough to record
-the list of file names and which version belongs to the snapshot.  Thus,
-you need not hesitate to create snapshots whenever they are useful.
+Tags are inexpensive, so you need not hesitate to create them whenever
+they are useful.  Branches vary in cost depending on your VCS; in
+older ones they may be expensive.
 
-  You can give a snapshot name as an argument to @kbd{C-x v =} or
+  You can give a tag or branch name as an argument to @kbd{C-x v =} or
 @kbd{C-x v ~}
 @iftex
 (@pxref{Old Revisions,,,emacs, the Emacs Manual}).
@@ -256,50 +262,40 @@ you need not hesitate to create snapshots whenever they are useful.
 @ifnottex
 (@pxref{Old Revisions}).
 @end ifnottex
-Thus, you can use it to compare a snapshot against the current files,
-or two snapshots against each other, or a snapshot against a named
-version.
-
-@node Snapshot Caveats
-@subsubsection Snapshot Caveats
-
-@cindex named configurations (RCS)
-  VC's snapshot facilities are modeled on RCS's named-configuration
-support.  They use RCS's native facilities for this, so
-snapshots made using RCS through VC are visible even when you bypass VC.
-
-  With CVS, Meta-CVS, and Subversion, VC also uses the native
-mechanism provided by that back end to make snapshots and retrieve them
-(@dfn{tags} for CVS and Meta-CVS, @dfn{copies} for Subversion).
-
-@c worded verbosely to avoid overfull hbox.
-  For SCCS, VC implements snapshots itself.  The files it uses contain
-name/file/version-number triples.  These snapshots are visible only
-through VC.
-
-  There is no support for VC snapshots using GNU Arch yet.
-
-  A snapshot is a set of checked-in versions.  So make sure that all the
-files are checked in and not locked when you make a snapshot.
-
-  File renaming and deletion can create some difficulties with snapshots.
-This is not a VC-specific problem, but a general design issue in version
-control systems that no one has solved very well yet.
-
-  If you rename a registered file, you need to rename its master along
-with it (the command @code{vc-rename-file} does this automatically).  If
-you are using SCCS, you must also update the records of the snapshot, to
-mention the file by its new name (@code{vc-rename-file} does this,
-too).  An old snapshot that refers to a master file that no longer
-exists under the recorded name is invalid; VC can no longer retrieve
-it.  It would be beyond the scope of this manual to explain enough about
-RCS and SCCS to explain how to update the snapshots by hand.
-
-  Using @code{vc-rename-file} makes the snapshot remain valid for
+Thus, you can use it to compare a tagged version against the current files,
+or two tagged versions against each other.
+
+@node Revision Tag Caveats
+@subsubsection Revision Tag Caveats
+
+  For SCCS, VC implements tags itself; these tags are visible only
+through VC.  Most later systems (including CVS, Subversion, bzr, git,
+and hg) have a native tag facility, and VC uses it where
+available; those tags will be visible even when you bypass VC.
+
+  There is no support for VC tags using GNU Arch yet.
+
+  Under older VCSes (SCCS, RCS, CVS, early versions of Subversion),
+renaming and deletion could create some difficulties with tags.  This is
+not a VC-specific problem, but a general design issue in version
+control systems that was not solved effectively until the earliest
+third-generation systems.
+
+  In a file-oriented VCS, when you rename a registered file you need
+to rename its master along with it; the command @code{vc-rename-file}
+will do this automatically.  If you are using SCCS, you must also
+update the records of the tag, to mention the file by its new name
+(@code{vc-rename-file} does this, too).  An old tag that refers to a
+master file that no longer exists under the recorded name is invalid;
+VC can no longer retrieve it.  It would be beyond the scope of this
+manual to explain enough about RCS and SCCS to explain how to update
+the tags by hand.
+
+  Using @code{vc-rename-file} makes the tag remain valid for
 retrieval, but it does not solve all problems.  For example, some of the
 files in your program probably refer to others by name.  At the very
 least, the makefile probably mentions the file that you renamed.  If you
-retrieve an old snapshot, the renamed file is retrieved under its new
+retrieve an old tag, the renamed file is retrieved under its new
 name, which is not the name that the makefile expects.  So the program
 won't really work as retrieved.
 
@@ -473,10 +469,9 @@ to avoid putting such trivia into @file{ChangeLog}.
   When you rename a registered file, you must also rename its master
 file correspondingly to get proper results.  Use @code{vc-rename-file}
 to rename the source file as you specify, and rename its master file
-accordingly.  It also updates any snapshots (@pxref{Snapshots}) that
+accordingly.  It also updates any tags (@pxref{Revision Tags}) that
 mention the file, so that they use the new name; despite this, the
-snapshot thus modified may not completely work (@pxref{Snapshot
-Caveats}).
+tag thus modified may not completely work (@pxref{Revision Tag Caveats}).
 
   Some back ends do not provide an explicit rename operation to their
 repositories.  After issuing @code{vc-rename-file}, use @kbd{C-x v v}
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 5de6777ff33..d3d736594bf 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,10 @@
 2008-05-15  Eric S. Raymond  <esr@snark.thyrsus.com>
 
+	* vc-cvs.el, vc-git.el, vc-hg.el, vc-hooks.el, vc-mcvs.el,
+	vc-rcs.el, vc-sccs.el, vc-svn.el, vc.el: Rename
+	vc-*-create-snapshot and vc-*-retrieve-snapshot to vc-*-create-tag
+	and vc-*-retireve-tag respectively.
+
 	* vc-dispatcher.el: Fix an incorrect buffer name and remove an
 	unneeded defalias.
 
diff --git a/lisp/vc-cvs.el b/lisp/vc-cvs.el
index 41372debcf0..90a6b7b2e1f 100644
--- a/lisp/vc-cvs.el
+++ b/lisp/vc-cvs.el
@@ -622,19 +622,19 @@ systime, or nil if there is none."
       nil)))
 
 ;;;
-;;; Snapshot system
+;;; Tag system
 ;;;
 
-(defun vc-cvs-create-snapshot (dir name branchp)
+(defun vc-cvs-create-tag (dir name branchp)
   "Assign to DIR's current revision a given NAME.
 If BRANCHP is non-nil, the name is created as a branch (and the current
 workspace is immediately moved to that new branch)."
   (vc-cvs-command nil 0 dir "tag" "-c" (if branchp "-b") name)
   (when branchp (vc-cvs-command nil 0 dir "update" "-r" name)))
 
-(defun vc-cvs-retrieve-snapshot (dir name update)
-  "Retrieve a snapshot at and below DIR.
-NAME is the name of the snapshot; if it is empty, do a `cvs update'.
+(defun vc-cvs-retrieve-tag (dir name update)
+  "Retrieve a tag at and below DIR.
+NAME is the name of the tag; if it is empty, do a `cvs update'.
 If UPDATE is non-nil, then update (resynch) any affected buffers."
   (with-current-buffer (get-buffer-create "*vc*")
     (let ((default-directory dir)
diff --git a/lisp/vc-git.el b/lisp/vc-git.el
index b4704efc61e..4a5b7ab8403 100644
--- a/lisp/vc-git.el
+++ b/lisp/vc-git.el
@@ -43,37 +43,39 @@
 ;; beginning of vc.el. The current status is:
 ;; ("??" means: "figure out what to do about it")
 ;;
-;; FUNCTION NAME                                   STATUS
+;; FUNCTION NAME                        STATUS
 ;; BACKEND PROPERTIES
-;; * revision-granularity                          OK
+;; * revision-granularity                      OK
 ;; STATE-QUERYING FUNCTIONS
-;; * registered (file)				   OK
+;; * registered (file)			   OK
 ;; * state (file)				   OK
 ;; - state-heuristic (file)			   NOT NEEDED
-;; * working-revision (file)			   OK
-;; - latest-on-branch-p (file)			   NOT NEEDED
-;; * checkout-model (files)			   OK
+;; * working-revision (file)		   OK
+;; - latest-on-branch-p (file)		   NOT NEEDED
+;; * checkout-model (files)		   OK
 ;; - workfile-unchanged-p (file)		   OK
 ;; - mode-line-string (file)			   OK
-;; - prettify-state-info (file)			   OK
+;; - prettify-state-info (file)		   OK
 ;; STATE-CHANGING FUNCTIONS
-;; * create-repo ()				   OK
-;; * register (files &optional rev comment)	   OK
+;; * create-repo ()			   OK
+;; * register (files &optional rev comment)    OK
 ;; - init-revision (file)			   NOT NEEDED
 ;; - responsible-p (file)			   OK
 ;; - could-register (file)			   NOT NEEDED, DEFAULT IS GOOD
 ;; - receive-file (file rev)			   NOT NEEDED
-;; - unregister (file)				   OK
+;; - unregister (file)			   OK
 ;; * checkin (files rev comment)		   OK
 ;; * find-revision (file rev buffer)		   OK
 ;; * checkout (file &optional editable rev)	   OK
 ;; * revert (file &optional contents-done)	   OK
-;; - rollback (files)				   COULD BE SUPPORTED
-;; - merge (file rev1 rev2)			   It would be possible to merge changes into
-;;                                                 a single file, but when committing they
-;;                                                 wouldn't be identified as a merge by git,
-;;                                                 so it's probably not a good idea.
-;; - merge-news (file)				   see `merge'
+;; - rollback (files)			   COULD BE SUPPORTED
+;; - merge (file rev1 rev2)                   It would be possible to merge
+;;                                          changes into a single file, but when
+;;                                          committing they wouldn't
+;;                                          be identified as a merge
+;;                                          by git, so it's probably
+;;                                          not a good idea.
+;; - merge-news (file)			   see `merge'
 ;; - steal-lock (file &optional revision)	   NOT NEEDED
 ;; HISTORY FUNCTIONS
 ;; * print-log (files &optional buffer)		   OK
@@ -81,27 +83,26 @@
 ;; - show-log-entry (revision)			   OK
 ;; - comment-history (file)			   ??
 ;; - update-changelog (files)			   COULD BE SUPPORTED
-;; * diff (file &optional rev1 rev2 buffer)	   OK
+;; * diff (file &optional rev1 rev2 buffer)	           OK
 ;; - revision-completion-table (files)		   OK
 ;; - annotate-command (file buf &optional rev)	   OK
 ;; - annotate-time ()				   OK
 ;; - annotate-current-time ()			   NOT NEEDED
-;; - annotate-extract-revision-at-line ()	   OK
-;; SNAPSHOT SYSTEM
-;; - create-snapshot (dir name branchp)		   OK
-;; - assign-name (file name)			   NOT NEEDED
-;; - retrieve-snapshot (dir name update)	   OK, needs to update buffers
+;; - annotate-extract-revision-at-line ()	           OK
+;; TAG SYSTEM
+;; - create-tag (dir name branchp)	   OK
+;; - retrieve-tag (dir name update)	   OK, needs to update buffers
 ;; MISCELLANEOUS
-;; - make-version-backups-p (file)		   NOT NEEDED
-;; - repository-hostname (dirname)		   NOT NEEDED
+;; - make-version-backups-p (file)	   NOT NEEDED
+;; - repository-hostname (dirname)	   NOT NEEDED
 ;; - previous-revision (file rev)		   OK
-;; - next-revision (file rev)			   OK
-;; - check-headers ()				   COULD BE SUPPORTED
-;; - clear-headers ()				   NOT NEEDED
-;; - delete-file (file)				   OK
-;; - rename-file (old new)			   OK
-;; - find-file-hook ()				   NOT NEEDED
-;; - find-file-not-found-hook ()                   NOT NEEDED
+;; - next-revision (file rev)		   OK
+;; - check-headers ()			   COULD BE SUPPORTED
+;; - clear-headers ()			   NOT NEEDED
+;; - delete-file (file)			   OK
+;; - rename-file (old new)		   OK
+;; - find-file-hook ()			   NOT NEEDED
+;; - find-file-not-found-hook ()                NOT NEEDED
 
 (eval-when-compile
   (require 'cl)
@@ -554,16 +555,16 @@ or BRANCH^ (where \"^\" can be repeated)."
     (and (looking-at "[0-9a-f^][0-9a-f]+")
          (buffer-substring-no-properties (match-beginning 0) (match-end 0)))))
 
-;;; SNAPSHOT SYSTEM
+;;; TAG SYSTEM
 
-(defun vc-git-create-snapshot (dir name branchp)
+(defun vc-git-create-tag (dir name branchp)
   (let ((default-directory dir))
     (and (vc-git-command nil 0 nil "update-index" "--refresh")
          (if branchp
              (vc-git-command nil 0 nil "checkout" "-b" name)
            (vc-git-command nil 0 nil "tag" name)))))
 
-(defun vc-git-retrieve-snapshot (dir name update)
+(defun vc-git-retrieve-tag (dir name update)
   (let ((default-directory dir))
     (vc-git-command nil 0 nil "checkout" name)
     ;; FIXME: update buffers if `update' is true
diff --git a/lisp/vc-hg.el b/lisp/vc-hg.el
index baa60589f9a..6b025c8cfa7 100644
--- a/lisp/vc-hg.el
+++ b/lisp/vc-hg.el
@@ -76,10 +76,9 @@
 ;; - annotate-time ()                          OK
 ;; - annotate-current-time ()                  NOT NEEDED
 ;; - annotate-extract-revision-at-line ()      OK
-;; SNAPSHOT SYSTEM
-;; - create-snapshot (dir name branchp)        NEEDED (probably branch?)
-;; - assign-name (file name)                   NOT NEEDED
-;; - retrieve-snapshot (dir name update)       ?? NEEDED??
+;; TAG SYSTEM
+;; - create-tag (dir name branchp)       NEEDED
+;; - retrieve-tag (dir name update)       NEEDED
 ;; MISCELLANEOUS
 ;; - make-version-backups-p (file)             ??
 ;; - repository-hostname (dirname)             ??
diff --git a/lisp/vc-hooks.el b/lisp/vc-hooks.el
index ed44eba3498..738cf257562 100644
--- a/lisp/vc-hooks.el
+++ b/lisp/vc-hooks.el
@@ -981,8 +981,8 @@ Used in `find-file-not-found-functions'."
     (define-key map "i" 'vc-register)
     (define-key map "l" 'vc-print-log)
     (define-key map "m" 'vc-merge)
-    (define-key map "r" 'vc-retrieve-snapshot)
-    (define-key map "s" 'vc-create-snapshot)
+    (define-key map "r" 'vc-retrieve-tag)
+    (define-key map "s" 'vc-create-tag)
     (define-key map "u" 'vc-revert)
     (define-key map "v" 'vc-next-action)
     (define-key map "+" 'vc-update)
@@ -996,12 +996,12 @@ Used in `find-file-not-found-functions'."
   (let ((map (make-sparse-keymap "Version Control")))
     ;;(define-key map [show-files]
     ;;  '("Show Files under VC" . (vc-directory t)))
-    (define-key map [vc-retrieve-snapshot]
-      '(menu-item "Retrieve Snapshot" vc-retrieve-snapshot
-		  :help "Retrieve snapshot"))
-    (define-key map [vc-create-snapshot]
-      '(menu-item "Create Snapshot" vc-create-snapshot
-		  :help "Create Snapshot"))
+    (define-key map [vc-retrieve-tag]
+      '(menu-item "Retrieve Tag" vc-retrieve-tag
+		  :help "Retrieve tagged version or branch"))
+    (define-key map [vc-create-tag]
+      '(menu-item "Create Tag" vc-create-tag
+		  :help "Create version tag"))
     (define-key map [separator1] '("----"))
     (define-key map [vc-annotate]
       '(menu-item "Annotate" vc-annotate
diff --git a/lisp/vc-mcvs.el b/lisp/vc-mcvs.el
index dfe3bb1d1f9..32c7b99b41b 100644
--- a/lisp/vc-mcvs.el
+++ b/lisp/vc-mcvs.el
@@ -48,7 +48,7 @@
 
 ;;; Bugs:
 
-;; - Retrieving snapshots doesn't filter `cvs update' output and thus
+;; - Retrieving tags doesn't filter `cvs update' output and thus
 ;;   parses bogus filenames.  Don't know if it harms.
 
 ;;; Code:
@@ -461,10 +461,10 @@ Optional arg REVISION is a revision to annotate from."
 (defalias 'vc-mcvs-annotate-time 'vc-cvs-annotate-time)
 
 ;;;
-;;; Snapshot system
+;;; Tag system
 ;;;
 
-(defun vc-mcvs-create-snapshot (dir name branchp)
+(defun vc-mcvs-create-tag (dir name branchp)
   "Assign to DIR's current revision a given NAME.
 If BRANCHP is non-nil, the name is created as a branch (and the current
 workspace is immediately moved to that new branch)."
@@ -473,9 +473,9 @@ workspace is immediately moved to that new branch)."
     (vc-mcvs-command nil 0 dir "branch" name)
     (vc-mcvs-command nil 0 dir "switch" name)))
 
-(defun vc-mcvs-retrieve-snapshot (dir name update)
-  "Retrieve a snapshot at and below DIR.
-NAME is the name of the snapshot; if it is empty, do a `cvs update'.
+(defun vc-mcvs-retrieve-tag (dir name update)
+  "Retrieve a tag at and below DIR.
+NAME is the name of the tag; if it is empty, do a `cvs update'.
 If UPDATE is non-nil, then update (resynch) any affected buffers."
   (with-current-buffer (get-buffer-create "*vc*")
     (let ((default-directory dir)
diff --git a/lisp/vc-rcs.el b/lisp/vc-rcs.el
index 14a091c4a6f..bda6aec95c2 100644
--- a/lisp/vc-rcs.el
+++ b/lisp/vc-rcs.el
@@ -787,12 +787,19 @@ systime, or nil if there is none.  Also, reposition point."
 
 
 ;;;
-;;; Snapshot system
+;;; Tag system
 ;;;
 
-(defun vc-rcs-assign-name (file name)
-  "Assign to FILE's latest version a given NAME."
-  (vc-do-command "*vc*" 0 "rcs" (vc-name file) (concat "-n" name ":")))
+(defun vc-rcs-create-tag (backend dir name branchp)
+  (when branchp
+    (error "RCS backend %s does not support module branches."))
+  (let ((result (vc-tag-precondition dir)))
+    (if (stringp result)
+	(error "File %s is not up-to-date" result)
+      (vc-file-tree-walk
+       dir
+       (lambda (f)
+	 (vc-do-command "*vc*" 0 "rcs" (vc-name f) (concat "-n" name ":")))))))
 
 
 ;;;
diff --git a/lisp/vc-sccs.el b/lisp/vc-sccs.el
index f8a98f52702..a5096da9643 100644
--- a/lisp/vc-sccs.el
+++ b/lisp/vc-sccs.el
@@ -352,12 +352,20 @@ revert all subfiles."
 
 
 ;;;
-;;; Snapshot system
+;;; Tag system.  SCCS doesn't have tags, so we simulate them by maintaining
+;;; our own set of name-to-revision mappings.
 ;;;
 
-(defun vc-sccs-assign-name (file name)
-  "Assign to FILE's latest revision a given NAME."
-  (vc-sccs-add-triple name file (vc-working-revision file)))
+(defun vc-sccs-create-tag (backend dir name branchp)
+  (when branchp
+    (error "SCCS backend %s does not support module branches."))
+  (let ((result (vc-tag-precondition dir)))
+    (if (stringp result)
+	(error "File %s is not up-to-date" result)
+      (vc-file-tree-walk
+       dir
+       (lambda (f)
+	 (vc-sccs-add-triple name f (vc-working-revision f)))))))
 
 
 ;;;
@@ -373,7 +381,7 @@ revert all subfiles."
 (defun vc-sccs-rename-file (old new)
   ;; Move the master file (using vc-rcs-master-templates).
   (vc-rename-master (vc-name old) new vc-sccs-master-templates)
-  ;; Update the snapshot file.
+  ;; Update the tag file.
   (with-current-buffer
       (find-file-noselect
        (expand-file-name vc-sccs-name-assoc-file
@@ -446,7 +454,7 @@ The result is a list of the form ((REVISION . USER) (REVISION . USER) ...)."
     (kill-buffer (current-buffer))))
 
 (defun vc-sccs-lookup-triple (file name)
-  "Return the numeric revision corresponding to a named snapshot of FILE.
+  "Return the numeric revision corresponding to a named tag of FILE.
 If NAME is nil or a revision number string it's just passed through."
   (if (or (null name)
 	  (let ((firstchar (aref name 0)))
diff --git a/lisp/vc-svn.el b/lisp/vc-svn.el
index 44f7e8eb44d..0b0828ac23d 100644
--- a/lisp/vc-svn.el
+++ b/lisp/vc-svn.el
@@ -465,20 +465,20 @@ or svn+ssh://."
 	(buffer-size (get-buffer buffer)))))
 
 ;;;
-;;; Snapshot system
+;;; Tag system
 ;;;
 
-(defun vc-svn-create-snapshot (dir name branchp)
+(defun vc-svn-create-tag (dir name branchp)
   "Assign to DIR's current revision a given NAME.
 If BRANCHP is non-nil, the name is created as a branch (and the current
 workspace is immediately moved to that new branch).
 NAME is assumed to be a URL."
   (vc-svn-command nil 0 dir "copy" name)
-  (when branchp (vc-svn-retrieve-snapshot dir name nil)))
+  (when branchp (vc-svn-retrieve-tag dir name nil)))
 
-(defun vc-svn-retrieve-snapshot (dir name update)
-  "Retrieve a snapshot at and below DIR.
-NAME is the name of the snapshot; if it is empty, do a `svn update'.
+(defun vc-svn-retrieve-tag (dir name update)
+  "Retrieve a tag at and below DIR.
+NAME is the name of the tag; if it is empty, do a `svn update'.
 If UPDATE is non-nil, then update (resynch) any affected buffers.
 NAME is assumed to be a URL."
   (vc-svn-command nil 0 dir "switch" name)
diff --git a/lisp/vc.el b/lisp/vc.el
index 7f355a6c38a..57f8f092d0e 100644
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -438,28 +438,23 @@
 ;;   corresponding to the current line, or nil if there is no revision
 ;;   corresponding to the current line.
 ;;
-;; SNAPSHOT SYSTEM
+;; TAG SYSTEM
 ;;
-;; - create-snapshot (dir name branchp)
+;; - create-tag (dir name branchp)
 ;;
-;;   Take a snapshot of the current state of files under DIR and name it
-;;   NAME.  This should make sure that files are up-to-date before
-;;   proceeding with the action.  DIR can also be a file and if BRANCHP
-;;   is specified, NAME should be created as a branch and DIR should be
-;;   checked out under this new branch.  The default implementation does
-;;   not support branches but does a sanity check, a tree traversal and
-;;   for each file calls `assign-name'.
+;;   Attach the tag NAME to the state of the working copy.  This
+;;   should make sure that files are up-to-date before proceeding with
+;;   the action.  DIR can also be a file and if BRANCHP is specified,
+;;   NAME should be created as a branch and DIR should be checked out
+;;   under this new branch.  The default implementation does not
+;;   support branches but does a sanity check, a tree traversal and
+;;   assigns the tag to each file.
 ;;
-;; - assign-name (file name)
+;; - retrieve-tag (dir name update)
 ;;
-;;   Give name NAME to the working revision of FILE, assuming it is
-;;   up-to-date.  Only used by the default version of `create-snapshot'.
-;;
-;; - retrieve-snapshot (dir name update)
-;;
-;;   Retrieve a named snapshot of all registered files at or below DIR.
+;;   Retrieve the version tagged by NAME of all registered files at or below DIR.
 ;;   If UPDATE is non-nil, then update buffers of any files in the
-;;   snapshot that are currently visited.  The default implementation
+;;   tag that are currently visited.  The default implementation
 ;;   does a sanity check whether there aren't any uncommitted changes at
 ;;   or below DIR, and then performs a tree walk, using the `checkout'
 ;;   function to retrieve the corresponding revisions.
@@ -570,8 +565,6 @@
 ;;
 ;;;; Improved branch and tag handling:
 ;;
-;; - "snapshots" should be renamed to "tags", and thoroughly reworked.
-;;
 ;; - add a generic mechanism for remembering the current branch names,
 ;;   display the branch name in the mode-line. Replace
 ;;   vc-cvs-sticky-tag with that.
@@ -580,7 +573,7 @@
 ;;   adapted accordingly.  Also, it considers RCS and CVS to be the same, 
 ;;   which is pretty confusing.
 ;;
-;; - vc-create-snapshot and vc-retrieve-snapshot should update the
+;; - vc-create-tag and vc-retrieve-tag should update the
 ;;   buffers that might be visiting the affected files.
 ;;
 ;;;; Default Behavior:
@@ -2047,10 +2040,10 @@ outside of VC) and one wants to do some operation on it."
 
 ;; Named-configuration entry points
 
-(defun vc-snapshot-precondition (dir)
+(defun vc-tag-precondition (dir)
   "Scan the tree below DIR, looking for files not up-to-date.
 If any file is not up-to-date, return the name of the first such file.
-\(This means, neither snapshot creation nor retrieval is allowed.\)
+\(This means, neither tag creation nor retrieval is allowed.\)
 If one or more of the files are currently visited, return `visited'.
 Otherwise, return nil."
   (let ((status nil))
@@ -2063,40 +2056,40 @@ Otherwise, return nil."
       status)))
 
 ;;;###autoload
-(defun vc-create-snapshot (dir name branchp)
-  "Descending recursively from DIR, make a snapshot called NAME.
+(defun vc-create-tag (dir name branchp)
+  "Descending recursively from DIR, make a tag called NAME.
 For each registered file, the working revision becomes part of
 the named configuration.  If the prefix argument BRANCHP is
-given, the snapshot is made as a new branch and the files are
+given, the tag is made as a new branch and the files are
 checked out in that new branch."
   (interactive
    (list (read-file-name "Directory: " default-directory default-directory t)
-         (read-string "New snapshot name: ")
+         (read-string "New tag name: ")
 	 current-prefix-arg))
-  (message "Making %s... " (if branchp "branch" "snapshot"))
+  (message "Making %s... " (if branchp "branch" "tag"))
   (when (file-directory-p dir) (setq dir (file-name-as-directory dir)))
   (vc-call-backend (vc-responsible-backend dir)
-		   'create-snapshot dir name branchp)
-  (message "Making %s... done" (if branchp "branch" "snapshot")))
+		   'create-tag dir name branchp)
+  (message "Making %s... done" (if branchp "branch" "tag")))
 
 ;;;###autoload
-(defun vc-retrieve-snapshot (dir name)
-  "Descending recursively from DIR, retrieve the snapshot called NAME.
+(defun vc-retrieve-tag (dir name)
+  "Descending recursively from DIR, retrieve the tag called NAME.
 If NAME is empty, it refers to the latest revisions.
 If locking is used for the files in DIR, then there must not be any
 locked files at or below DIR (but if NAME is empty, locked files are
 allowed and simply skipped)."
   (interactive
    (list (read-file-name "Directory: " default-directory default-directory t)
-         (read-string "Snapshot name to retrieve (default latest revisions): ")))
+         (read-string "Tag name to retrieve (default latest revisions): ")))
   (let ((update (yes-or-no-p "Update any affected buffers? "))
 	(msg (if (or (not name) (string= name ""))
 		 (format "Updating %s... " (abbreviate-file-name dir))
-	       (format "Retrieving snapshot into %s... "
+	       (format "Retrieving tag into %s... "
 		       (abbreviate-file-name dir)))))
     (message "%s" msg)
     (vc-call-backend (vc-responsible-backend dir)
-		     'retrieve-snapshot dir name update)
+		     'retrieve-tag dir name update)
     (message "%s" (concat msg "done"))))
 
 ;; Miscellaneous other entry points
@@ -2693,18 +2686,7 @@ to provide the `find-revision' operation instead."
   "Let BACKEND receive FILE from another version control system."
   (vc-call-backend backend 'register file rev ""))
 
-(defun vc-default-create-snapshot (backend dir name branchp)
-  (when branchp
-    (error "VC backend %s does not support module branches" backend))
-  (let ((result (vc-snapshot-precondition dir)))
-    (if (stringp result)
-	(error "File %s is not up-to-date" result)
-      (vc-file-tree-walk
-       dir
-       (lambda (f)
-	 (vc-call-backend backend 'assign-name f name))))))
-
-(defun vc-default-retrieve-snapshot (backend dir name update)
+(defun vc-default-retrieve-tag (backend dir name update)
   (if (string= name "")
       (progn
         (vc-file-tree-walk
@@ -2714,7 +2696,7 @@ to provide the `find-revision' operation instead."
 		 (vc-error-occurred
 		  (vc-call-backend backend 'checkout f nil "")
 		  (when update (vc-resynch-buffer f t t)))))))
-    (let ((result (vc-snapshot-precondition dir)))
+    (let ((result (vc-tag-precondition dir)))
       (if (stringp result)
           (error "File %s is locked" result)
         (setq update (and (eq result 'visited) update))
@@ -3290,7 +3272,7 @@ Invoke FUNC f ARGS on each VC-managed file f underneath it."
 ;; The performance problem, it turns out, simplifies in practice to the
 ;; problem of making vc-state fast.  The two other functions that call
 ;; prs/rlog will not be so commonly used that the slowdown is a problem; one
-;; makes snapshots, the other deletes the calling user's last change in the
+;; makes tags, the other deletes the calling user's last change in the
 ;; master.
 ;;
 ;; The race condition implies that we have to either (a) lock the master