vc/vc-arch.el: Moved to obsolete directory...

...so a test framework won't trip over bit-rot in it.  There has been no
Arch snapshot for nine years.

1 files changed, 644 insertions, 0 deletions

diff --git a/lisp/obsolete/vc-arch.el b/lisp/obsolete/vc-arch.el
new file mode 100644
index 00000000000..d1344f2b1cc
--- /dev/null
+++ b/lisp/obsolete/vc-arch.el
@@ -0,0 +1,644 @@
+;;; vc-arch.el --- VC backend for the Arch version-control system  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2004-2014 Free Software Foundation, Inc.
+
+;; Author:      FSF (see vc.el for full credits)
+;; Maintainer:  Stefan Monnier <monnier@gnu.org>
+;; Package: vc
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; The home page of the Arch version control system is at
+;;
+;;      http://www.gnuarch.org/
+;;
+;; This is derived from vc-mcvs.el as follows:
+;; - cp vc-mcvs.el vc-arch.el and then M-% mcvs RET arch RET
+;;
+;; Then of course started the hacking.
+;;
+;; What has been partly tested:
+;; - Open a file.
+;; - C-x v =  without any prefix arg.
+;; - C-x v v  to commit a change to a single file.
+
+;; Bugs:
+
+;; - *vc-log*'s initial content lacks the `Summary:' lines.
+;; - All files under the tree are considered as "under Arch's control"
+;;   without regards to =tagging-method and such.
+;; - Files are always considered as `edited'.
+;; - C-x v l does not work.
+;; - C-x v i does not work.
+;; - C-x v ~ does not work.
+;; - C-x v u does not work.
+;; - C-x v s does not work.
+;; - C-x v r does not work.
+;; - VC directory listings do not work.
+;; - And more...
+
+;;; Code:
+
+(eval-when-compile (require 'vc))
+
+;;; Properties of the backend
+
+(defun vc-arch-revision-granularity () 'repository)
+(defun vc-arch-checkout-model (_files) 'implicit)
+
+;;;
+;;; Customization options
+;;;
+
+(defgroup vc-arch nil
+  "VC Arch backend."
+  :version "24.1"
+  :group 'vc)
+
+;; It seems Arch diff does not accept many options, so this is not
+;; very useful.  It exists mainly so that the VC backends are all
+;; consistent with regards to their treatment of diff switches.
+(defcustom vc-arch-diff-switches t
+  "String or list of strings specifying switches for Arch diff under VC.
+If nil, use the value of `vc-diff-switches'.  If t, use no switches."
+  :type '(choice (const :tag "Unspecified" nil)
+                 (const :tag "None" t)
+                 (string :tag "Argument String")
+                 (repeat :tag "Argument List" :value ("") string))
+  :version "23.1"
+  :group 'vc-arch)
+
+(define-obsolete-variable-alias 'vc-arch-command 'vc-arch-program "23.1")
+
+(defcustom vc-arch-program
+  (let ((candidates '("tla" "baz")))
+    (while (and candidates (not (executable-find (car candidates))))
+      (setq candidates (cdr candidates)))
+    (or (car candidates) "tla"))
+  "Name of the Arch executable."
+  :type 'string
+  :group 'vc-arch)
+
+;; Clear up the cache to force vc-call to check again and discover
+;; new functions when we reload this file.
+(put 'Arch 'vc-functions nil)
+
+;;;###autoload (defun vc-arch-registered (file)
+;;;###autoload   (if (vc-find-root file "{arch}/=tagging-method")
+;;;###autoload       (progn
+;;;###autoload         (load "vc-arch" nil t)
+;;;###autoload         (vc-arch-registered file))))
+
+(defun vc-arch-add-tagline ()
+  "Add an `arch-tag' to the end of the current file."
+  (interactive)
+  (comment-normalize-vars)
+  (goto-char (point-max))
+  (forward-comment -1)
+  (skip-chars-forward " \t\n")
+  (cond
+   ((not (bolp)) (insert "\n\n"))
+   ((not (eq ?\n (char-before (1- (point))))) (insert "\n")))
+  (let ((beg (point))
+        (idfile (and buffer-file-name
+                     (expand-file-name
+                      (concat ".arch-ids/"
+                              (file-name-nondirectory buffer-file-name)
+                              ".id")
+                      (file-name-directory buffer-file-name)))))
+    (insert "arch-tag: ")
+    (if (and idfile (file-exists-p idfile))
+        ;; If the file is unreadable, we do want to get an error here.
+        (progn
+          (insert-file-contents idfile)
+          (forward-line 1)
+          (delete-file idfile))
+      (condition-case nil
+          (call-process "uuidgen" nil t)
+        (file-error (insert (format "%s <%s> %s"
+                                    (current-time-string)
+                                    user-mail-address
+                                    (+ (nth 2 (current-time))
+                                       (buffer-size)))))))
+    (comment-region beg (point))))
+
+(defconst vc-arch-tagline-re "^\\W*arch-tag:[ \t]*\\(.*[^ \t\n]\\)")
+
+(defmacro vc-with-current-file-buffer (file &rest body)
+  (declare (indent 2) (debug t))
+  `(let ((-kill-buf- nil)
+         (-file- ,file))
+     (with-current-buffer (or (find-buffer-visiting -file-)
+                              (setq -kill-buf- (generate-new-buffer " temp")))
+       ;; Avoid find-file-literally since it can do many undesirable extra
+       ;; things (among which, call us back into an infinite loop).
+       (if -kill-buf- (insert-file-contents -file-))
+       (unwind-protect
+           (progn ,@body)
+         (if (buffer-live-p -kill-buf-) (kill-buffer -kill-buf-))))))
+
+(defun vc-arch-file-source-p (file)
+  "Can return nil, `maybe' or a non-nil value.
+Only the value `maybe' can be trusted :-(."
+  ;; FIXME: Check the tag and name of parent dirs.
+  (unless (string-match "\\`[,+]" (file-name-nondirectory file))
+    (or (string-match "\\`{arch}/"
+                      (file-relative-name file (vc-arch-root file)))
+        (file-exists-p
+         ;; Check the presence of an ID file.
+         (expand-file-name
+          (concat ".arch-ids/" (file-name-nondirectory file) ".id")
+          (file-name-directory file)))
+        ;; Check the presence of a tagline.
+        (vc-with-current-file-buffer file
+          (save-excursion
+            (goto-char (point-max))
+            (or (re-search-backward vc-arch-tagline-re (- (point) 1000) t)
+                (progn
+                  (goto-char (point-min))
+                  (re-search-forward vc-arch-tagline-re (+ (point) 1000) t)))))
+        ;; FIXME: check =tagging-method to see whether untagged files might
+        ;; be source or not.
+        (with-current-buffer
+            (find-file-noselect (expand-file-name "{arch}/=tagging-method"
+                                                  (vc-arch-root file)))
+          (let ((untagged-source t))    ;Default is `names'.
+            (save-excursion
+              (goto-char (point-min))
+              (if (re-search-forward "^[ \t]*\\(\\(tagline\\|implicit\\|names\\)\\|explicit\\)" nil t)
+                  (setq untagged-source (match-end 2)))
+              (if (re-search-forward "^[ \t]*untagged-source[ \t]+\\(\\(source\\)\\|precious\\|backup\\|junk\\|unrecognized\\)" nil t)
+                  (setq untagged-source (match-end 2))))
+            (if untagged-source 'maybe))))))
+
+(defun vc-arch-file-id (file)
+  ;; Don't include the kind of ID this is because it seems to be too messy.
+  (let ((idfile (expand-file-name
+                 (concat ".arch-ids/" (file-name-nondirectory file) ".id")
+                 (file-name-directory file))))
+    (if (file-exists-p idfile)
+        (with-temp-buffer
+          (insert-file-contents idfile)
+          (looking-at ".*[^ \n\t]")
+          (match-string 0))
+      (with-current-buffer (find-file-noselect file)
+        (save-excursion
+          (goto-char (point-max))
+          (if (or (re-search-backward vc-arch-tagline-re (- (point) 1000) t)
+                  (progn
+                    (goto-char (point-min))
+                    (re-search-forward vc-arch-tagline-re (+ (point) 1000) t)))
+              (match-string 1)
+            (concat "./" (file-relative-name file (vc-arch-root file)))))))))
+
+(defun vc-arch-tagging-method (file)
+  (with-current-buffer
+      (find-file-noselect
+       (expand-file-name "{arch}/=tagging-method" (vc-arch-root file)))
+    (save-excursion
+      (goto-char (point-min))
+      (if (re-search-forward
+           "^[ \t]*\\(tagline\\|implicit\\|names\\|explicit\\)" nil t)
+          (intern (match-string 1))
+        'names))))
+
+(defun vc-arch-root (file)
+  "Return the root directory of an Arch project, if any."
+  (or (vc-file-getprop file 'arch-root)
+      ;; Check the =tagging-method, in case someone naively manually
+      ;; creates a {arch} directory somewhere.
+      (let ((root (vc-find-root file "{arch}/=tagging-method")))
+        (when root
+          (vc-file-setprop
+           file 'arch-root root)))))
+
+(defun vc-arch-find-admin-dir (file)
+  "Return the administrative directory of FILE."
+  (expand-file-name "{arch}" (vc-arch-root file)))
+
+(defun vc-arch-register (files &optional _comment)
+  (dolist (file files)
+    (let ((tagmet (vc-arch-tagging-method file)))
+      (if (and (memq tagmet '(tagline implicit)) comment-start)
+          (with-current-buffer (find-file-noselect file)
+            (if (buffer-modified-p)
+                (error "Save %s first" (buffer-name)))
+            (vc-arch-add-tagline)
+            (save-buffer)))))
+  (vc-arch-command nil 0 files "add"))
+
+(defun vc-arch-registered (file)
+  ;; Don't seriously check whether it's source or not.  Checking would
+  ;; require running TLA, so it's better to not do it, so it also works if
+  ;; TLA is not installed.
+  (and (vc-arch-root file)
+       (vc-arch-file-source-p file)))
+
+(defun vc-arch-default-version (file)
+  (or (vc-file-getprop (vc-arch-root file) 'arch-default-version)
+      (let* ((root (vc-arch-root file))
+             (f (expand-file-name "{arch}/++default-version" root)))
+        (if (file-readable-p f)
+            (vc-file-setprop
+             root 'arch-default-version
+             (with-temp-buffer
+               (insert-file-contents f)
+               ;; Strip the terminating newline.
+               (buffer-substring (point-min) (1- (point-max)))))))))
+
+(defun vc-arch-state (file)
+  ;; There's no checkout operation and merging is not done from VC
+  ;; so the only operation that's state dependent that VC supports is commit
+  ;; which is only activated if the file is `edited'.
+  (let* ((root (vc-arch-root file))
+         (ver (vc-arch-default-version file))
+         (pat (concat "\\`" (subst-char-in-string ?/ ?% ver)))
+         (dir (expand-file-name ",,inode-sigs/"
+                                (expand-file-name "{arch}" root)))
+         (sigfile nil))
+    (dolist (f (if (file-directory-p dir) (directory-files dir t pat)))
+      (if (or (not sigfile) (file-newer-than-file-p f sigfile))
+          (setq sigfile f)))
+    (if (not sigfile)
+        'edited                         ;We know nothing.
+      (let ((id (vc-arch-file-id file)))
+        (setq id (replace-regexp-in-string "[ \t]" "_" id))
+        (with-current-buffer (find-file-noselect sigfile)
+          (goto-char (point-min))
+          (while (and (search-forward id nil 'move)
+                      (save-excursion
+                        (goto-char (- (match-beginning 0) 2))
+                        ;; For `names', the lines start with `?./foo/bar'.
+                        ;; For others there's 2 chars before the ./foo/bar.
+                        (or (not (or (bolp) (looking-at "\n?")))
+                            ;; Ignore E_ entries used for foo.id files.
+                            (looking-at "E_")))))
+          (if (eobp)
+              ;; ID not found.
+              (if (equal (file-name-nondirectory sigfile)
+                         (subst-char-in-string
+                          ?/ ?% (vc-arch-working-revision file)))
+                  'added
+                ;; Might be `added' or `up-to-date' as well.
+                ;; FIXME: Check in the patch logs to find out.
+                'edited)
+            ;; Found the ID, let's check the inode.
+            (if (not (re-search-forward
+                      "\t.*mtime=\\([0-9]+\\):size=\\([0-9]+\\)"
+                      (line-end-position) t))
+                ;; Buh?  Unexpected format.
+                'edited
+              (let ((ats (file-attributes file)))
+                (if (and (eq (nth 7 ats) (string-to-number (match-string 2)))
+                         (equal (format-time-string "%s" (nth 5 ats))
+                                (match-string 1)))
+                    'up-to-date
+                  'edited)))))))))
+
+;; dir-status-files called from vc-dir, which loads vc,
+;; which loads vc-dispatcher.
+(declare-function vc-exec-after "vc-dispatcher" (code))
+
+(defun vc-arch-dir-status-files (dir _files callback)
+  "Run 'tla inventory' for DIR and pass results to CALLBACK.
+CALLBACK expects (ENTRIES &optional MORE-TO-COME); see
+`vc-dir-refresh'."
+  (let ((default-directory dir))
+    (vc-arch-command t 'async nil "changes"))
+  ;; The updating could be done asynchronously.
+  (vc-run-delayed
+   (vc-arch-after-dir-status callback)))
+
+(defun vc-arch-after-dir-status (callback)
+  (let* ((state-map '(("M " . edited)
+                      ("Mb" . edited)   ;binary
+                      ("D " . removed)
+                      ("D/" . removed)  ;directory
+                      ("A " . added)
+                      ("A/" . added)    ;directory
+                      ("=>" . renamed)
+                      ("/>" . renamed)  ;directory
+                      ("lf" . symlink-to-file)
+                      ("fl" . file-to-symlink)
+                      ("--" . permissions-changed)
+                      ("-/" . permissions-changed) ;directory
+                      ))
+         (state-map-regexp (regexp-opt (mapcar 'car state-map) t))
+         (entry-regexp (concat "^" state-map-regexp " \\(.*\\)$"))
+         result)
+    (goto-char (point-min))
+    ;;(message "Got %s" (buffer-string))
+    (while (re-search-forward entry-regexp nil t)
+      (let* ((state-string (match-string 1))
+             (state (cdr (assoc state-string state-map)))
+             (filename (match-string 2)))
+        (push (list filename state) result)))
+
+    (funcall callback result nil)))
+
+(defun vc-arch-working-revision (file)
+  (let* ((root (expand-file-name "{arch}" (vc-arch-root file)))
+         (defbranch (vc-arch-default-version file)))
+    (when (and defbranch (string-match "\\`\\(.+@[^/\n]+\\)/\\(\\(\\(.*?\\)\\(?:--.*\\)?\\)--.*\\)\\'" defbranch))
+      (let* ((archive (match-string 1 defbranch))
+             (category (match-string 4 defbranch))
+             (branch (match-string 3 defbranch))
+             (version (match-string 2 defbranch))
+             (sealed nil) (rev-nb 0)
+             (rev nil)
+             logdir tmp)
+        (setq logdir (expand-file-name category root))
+        (setq logdir (expand-file-name branch logdir))
+        (setq logdir (expand-file-name version logdir))
+        (setq logdir (expand-file-name archive logdir))
+        (setq logdir (expand-file-name "patch-log" logdir))
+        (dolist (file (if (file-directory-p logdir) (directory-files logdir)))
+          ;; Revision names go: base-0, patch-N, version-0, versionfix-M.
+          (when (and (eq (aref file 0) ?v) (not sealed))
+            (setq sealed t rev-nb 0))
+          (if (and (string-match "-\\([0-9]+\\)\\'" file)
+                   (setq tmp (string-to-number (match-string 1 file)))
+                   (or (not sealed) (eq (aref file 0) ?v))
+                   (>= tmp rev-nb))
+              (setq rev-nb tmp rev file)))
+        ;; Use "none-000" if the tree hasn't yet been committed on the
+        ;; default branch.  We'll then get "Arch:000[branch]" on the mode-line.
+        (concat defbranch "--" (or rev "none-000"))))))
+
+
+(defcustom vc-arch-mode-line-rewrite
+  '(("\\`.*--\\(.*--.*\\)--\\(v?\\).*-\\([0-9]+\\)\\'" . "\\2\\3[\\1]"))
+  "Rewrite rules to shorten Arch's revision names on the mode-line."
+  :type '(repeat (cons regexp string))
+  :group 'vc-arch)
+
+(defun vc-arch-mode-line-string (file)
+  "Return a string for `vc-mode-line' to put in the mode line for FILE."
+  (let ((rev (vc-working-revision file)))
+    (dolist (rule vc-arch-mode-line-rewrite)
+      (if (string-match (car rule) rev)
+          (setq rev (replace-match (cdr rule) t nil rev))))
+    (format "Arch%c%s"
+            (pcase (vc-state file)
+              ((or `up-to-date `needs-update) ?-)
+              (`added ?@)
+              (t ?:))
+            rev)))
+
+(defun vc-arch-diff3-rej-p (rej)
+  (let ((attrs (file-attributes rej)))
+    (and attrs (< (nth 7 attrs) 60)
+         (with-temp-buffer
+           (insert-file-contents rej)
+           (goto-char (point-min))
+           (looking-at "Conflicts occurred, diff3 conflict markers left in file\\.")))))
+
+(defun vc-arch-delete-rej-if-obsolete ()
+  "For use in `after-save-hook'."
+  (save-excursion
+    (let ((rej (concat buffer-file-name ".rej")))
+      (when (and buffer-file-name (vc-arch-diff3-rej-p rej))
+        (unless (re-search-forward "^<<<<<<< " nil t)
+          ;; The .rej file is obsolete.
+          (condition-case nil (delete-file rej) (error nil))
+          ;; Remove the hook so that it is not called multiple times.
+          (remove-hook 'after-save-hook 'vc-arch-delete-rej-if-obsolete t))))))
+
+(defun vc-arch-find-file-hook ()
+  (let ((rej (concat buffer-file-name ".rej")))
+    (when (and buffer-file-name (file-exists-p rej))
+      (if (vc-arch-diff3-rej-p rej)
+          (save-excursion
+            (goto-char (point-min))
+            (if (not (re-search-forward "^<<<<<<< " nil t))
+                ;; The .rej file is obsolete.
+                (condition-case nil (delete-file rej) (error nil))
+              (smerge-mode 1)
+              (add-hook 'after-save-hook
+                        'vc-arch-delete-rej-if-obsolete nil t)
+              (message "There are unresolved conflicts in this file")))
+        (message "There are unresolved conflicts in %s"
+                 (file-name-nondirectory rej))))))
+
+(autoload 'vc-switches "vc")
+
+(defun vc-arch-checkin (files comment)
+  ;; FIXME: This implementation probably only works for singleton filesets
+  (let ((summary (file-relative-name (car files) (vc-arch-root (car files)))))
+    ;; Extract a summary from the comment.
+    (when (or (string-match "\\`Summary:[ \t]*\\(.*[^ \t\n]\\)\\([ \t]*\n\\)*" comment)
+              (string-match "\\`[ \t]*\\(.*[^ \t\n]\\)[ \t]*\\(\n?\\'\\|\n\\([ \t]*\n\\)+\\)" comment))
+      (setq summary (match-string 1 comment))
+      (setq comment (substring comment (match-end 0))))
+    (vc-arch-command nil 0 files "commit" "-s" summary "-L" comment "--"
+                     (vc-switches 'Arch 'checkin))))
+
+(defun vc-arch-diff (files &optional async oldvers newvers buffer)
+  "Get a difference report using Arch between two versions of FILES."
+  ;; FIXME: This implementation only works for singleton filesets.  To make
+  ;; it work for more cases, we have to either call `file-diffs' manually on
+  ;; each and every `file' in the fileset, or use `changes --diffs' (and
+  ;; variants) and maybe filter the output with `filterdiff' to only include
+  ;; the files in which we're interested.
+  (let ((file (car files)))
+    (if (and newvers
+             (vc-up-to-date-p file)
+             (equal newvers (vc-working-revision file)))
+        ;; Newvers is the base revision and the current file is unchanged,
+        ;; so we can diff with the current file.
+        (setq newvers nil))
+    (if newvers
+        (error "Diffing specific revisions not implemented")
+      (let* (process-file-side-effects
+             ;; Run the command from the root dir.
+             (default-directory (vc-arch-root file))
+             (status
+              (vc-arch-command
+               (or buffer "*vc-diff*")
+               (if async 'async 1)
+               nil "file-diffs"
+               (vc-switches 'Arch 'diff)
+               (file-relative-name file)
+               (if (equal oldvers (vc-working-revision file))
+                   nil
+                 oldvers))))
+        (if async 1 status)))))        ; async diff, pessimistic assumption.
+
+(defun vc-arch-delete-file (file)
+  (vc-arch-command nil 0 file "rm"))
+
+(defun vc-arch-rename-file (old new)
+  (vc-arch-command nil 0 new "mv" (file-relative-name old)))
+
+(defalias 'vc-arch-responsible-p 'vc-arch-root)
+
+(defun vc-arch-command (buffer okstatus file &rest flags)
+  "A wrapper around `vc-do-command' for use in vc-arch.el."
+  (apply 'vc-do-command (or buffer "*vc*") okstatus vc-arch-program file flags))
+
+;;; Completion of versions and revisions.
+
+(defun vc-arch--version-completion-table (root string)
+  (delq nil
+        (mapcar
+         (lambda (d)
+           (when (string-match "/\\([^/]+\\)/\\([^/]+\\)\\'" d)
+             (concat (match-string 2 d) "/" (match-string 1 d))))
+         (let ((default-directory root))
+           (file-expand-wildcards
+            (concat "*/*/"
+                    (if (string-match "/" string)
+                        (concat (substring string (match-end 0))
+                                "*/" (substring string 0 (match-beginning 0)))
+                      (concat "*/" string))
+                    "*"))))))
+
+(defun vc-arch-revision-completion-table (files)
+  (lambda (string pred action)
+    ;; FIXME: complete revision patches as well.
+    (let* ((root (expand-file-name "{arch}" (vc-arch-root (car files))))
+           (table (vc-arch--version-completion-table root string)))
+      (complete-with-action action table string pred))))
+
+;;; Trimming revision libraries.
+
+;; This code is not directly related to VC and there are many variants of
+;; this functionality available as scripts, but I like this version better,
+;; so maybe others will like it too.
+
+(defun vc-arch-trim-find-least-useful-rev (revs)
+  (let* ((first (pop revs))
+         (second (pop revs))
+         (third (pop revs))
+         ;; We try to give more importance to recent revisions.  The idea is
+         ;; that it's OK if checking out a revision 1000-patch-old is ten
+         ;; times slower than checking out a revision 100-patch-old.  But at
+         ;; the same time a 2-patch-old rev isn't really ten times more
+         ;; important than a 20-patch-old, so we use an arbitrary constant
+         ;; "100" to reduce this effect for recent revisions.  Making this
+         ;; constant a float has the side effect of causing the subsequent
+         ;; computations to be done as floats as well.
+         (max (+ 100.0 (car (or (car (last revs)) third))))
+         (cost (lambda () (/ (- (car third) (car first)) (- max (car second)))))
+         (minrev second)
+         (mincost (funcall cost)))
+    (while revs
+      (setq first second)
+      (setq second third)
+      (setq third (pop revs))
+      (when (< (funcall cost) mincost)
+        (setq minrev second)
+        (setq mincost (funcall cost))))
+    minrev))
+
+(defun vc-arch-trim-make-sentinel (revs)
+  (if (null revs) (lambda (_proc _msg) (message "VC-Arch trimming ... done"))
+    (lambda (_proc _msg)
+      (message "VC-Arch trimming %s..." (file-name-nondirectory (car revs)))
+      (rename-file (car revs) (concat (car revs) "*rm*"))
+      (let ((proc (start-process "vc-arch-trim" nil
+                                 "rm" "-rf" (concat (car revs) "*rm*"))))
+        (set-process-sentinel proc (vc-arch-trim-make-sentinel (cdr revs)))))))
+
+(defun vc-arch-trim-one-revlib (dir)
+  "Delete half of the revisions in the revision library."
+  (interactive "Ddirectory: ")
+  (let ((garbage (directory-files dir 'full "\\`,," 'nosort)))
+    (when garbage
+      (funcall (vc-arch-trim-make-sentinel garbage) nil nil)))
+  (let ((revs
+         (sort (delq nil
+                     (mapcar
+                      (lambda (f)
+                        (when (string-match "-\\([0-9]+\\)\\'" f)
+                          (cons (string-to-number (match-string 1 f)) f)))
+                      (directory-files dir nil nil 'nosort)))
+               'car-less-than-car))
+        (subdirs nil))
+    (when (cddr revs)
+      (dotimes (_i (/ (length revs) 2))
+        (let ((minrev (vc-arch-trim-find-least-useful-rev revs)))
+          (setq revs (delq minrev revs))
+          (push minrev subdirs)))
+      (funcall (vc-arch-trim-make-sentinel
+                (mapcar (lambda (x) (expand-file-name (cdr x) dir)) subdirs))
+               nil nil))))
+
+(defun vc-arch-trim-revlib ()
+  "Delete half of the revisions in the revision library."
+  (interactive)
+  (let ((rl-dir (with-output-to-string
+                  (call-process vc-arch-program nil standard-output nil
+                                "my-revision-library"))))
+    (while (string-match "\\(.*\\)\n" rl-dir)
+      (let ((dir (match-string 1 rl-dir)))
+        (setq rl-dir
+              (if (and (file-directory-p dir) (file-writable-p dir))
+                  dir
+                (substring rl-dir (match-end 0))))))
+    (unless (file-writable-p rl-dir)
+      (error "No writable revlib directory found"))
+    (message "Revlib at %s" rl-dir)
+    (let* ((archives (directory-files rl-dir 'full "[^.]\\|..."))
+           (categories
+            (apply 'append
+                   (mapcar (lambda (dir)
+                             (when (file-directory-p dir)
+                               (directory-files dir 'full "[^.]\\|...")))
+                           archives)))
+           (branches
+            (apply 'append
+                   (mapcar (lambda (dir)
+                             (when (file-directory-p dir)
+                               (directory-files dir 'full "[^.]\\|...")))
+                           categories)))
+           (versions
+            (apply 'append
+                   (mapcar (lambda (dir)
+                             (when (file-directory-p dir)
+                               (directory-files dir 'full "--.*--")))
+                           branches))))
+      (mapc 'vc-arch-trim-one-revlib versions))
+    ))
+
+(defvar vc-arch-extra-menu-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map [add-tagline]
+      '(menu-item "Add tagline" vc-arch-add-tagline))
+    map))
+
+(defun vc-arch-extra-menu () vc-arch-extra-menu-map)
+
+
+;;; Less obvious implementations.
+
+(defun vc-arch-find-revision (file rev buffer)
+  (let ((out (make-temp-file "vc-out")))
+    (unwind-protect
+        (progn
+          (with-temp-buffer
+            (vc-arch-command (current-buffer) 1 nil "file-diffs" file rev)
+            (call-process-region (point-min) (point-max)
+                                 "patch" nil nil nil "-R" "-o" out file))
+          (with-current-buffer buffer
+            (insert-file-contents out)))
+      (delete-file out))))
+
+(provide 'vc-arch)
+
+;;; vc-arch.el ends here