From ec402ad4328f5bb8bdfcbbad6c1c4a34f2ef5a8d Mon Sep 17 00:00:00 2001 From: Stefan Monnier Date: Wed, 11 Jul 2001 22:55:25 +0000 Subject: [PATCH] (vc-prefix-map): Moved back to vc-hooks.el. (vc-dired-mode-map): Fix the madness. --- lisp/ChangeLog | 8 + lisp/vc.el | 738 ++++++++++++++++++++++++------------------------- 2 files changed, 367 insertions(+), 379 deletions(-) diff --git a/lisp/ChangeLog b/lisp/ChangeLog index 277313b2fab..4dd4ea79a9f 100644 --- a/lisp/ChangeLog +++ b/lisp/ChangeLog @@ -1,3 +1,11 @@ +2001-07-11 Stefan Monnier + + * vc.el (vc-prefix-map): Moved back to vc-hooks.el. + (vc-dired-mode-map): Fix the madness. + + * vc-hooks.el (vc-mode): Dummy function for doc purposes. + (vc-prefix-map): Moved back from vc.el. + 2001-07-11 Gerd Moellmann * mail/mail-extr.el (mail-extr-all-top-level-domains): Increase diff --git a/lisp/vc.el b/lisp/vc.el index 2d879b32884..844eca88c68 100644 --- a/lisp/vc.el +++ b/lisp/vc.el @@ -5,7 +5,7 @@ ;; Author: FSF (see below for full credits) ;; Maintainer: Andre Spiegel -;; $Id: vc.el,v 1.298 2001/03/10 10:44:35 spiegel Exp $ +;; $Id: vc.el,v 1.299 2001/05/03 00:36:07 monnier Exp $ ;; This file is part of GNU Emacs. @@ -462,7 +462,7 @@ These are passed to the checkin program by \\[vc-register]." (defconst vc-maximum-comment-ring-size 32 "Maximum number of saved comments in the comment ring.") -;;; This is duplicated in diff.el. +;; This is duplicated in diff.el. (defvar diff-switches "-c" "*A string or list of strings specifying switches to be passed to diff.") @@ -592,27 +592,7 @@ and that its contents match what the master file says." :group 'vc) -;;; The main keymap - -(defvar vc-prefix-map - (let ((map (make-sparse-keymap))) - (define-key map "a" 'vc-update-change-log) - (define-key map "b" 'vc-switch-backend) - (define-key map "c" 'vc-cancel-version) - (define-key map "d" 'vc-directory) - (define-key map "g" 'vc-annotate) - (define-key map "h" 'vc-insert-headers) - (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 "u" 'vc-revert-buffer) - (define-key map "v" 'vc-next-action) - (define-key map "=" 'vc-diff) - (define-key map "~" 'vc-version-other-window) - map)) -(fset 'vc-prefix-map vc-prefix-map) +;; The main keymap ;; Initialization code, to be done just once at load-time (defvar vc-log-mode-map @@ -651,9 +631,9 @@ The keys are \(BUFFER . BACKEND\). See also `vc-annotate-get-backend'.") (defvar vc-comment-ring-index nil) (defvar vc-last-comment-match "") -;;; functions that operate on RCS revision numbers. This code should -;;; also be moved into the backends. It stays for now, however, since -;;; it is used in code below. +;; functions that operate on RCS revision numbers. This code should +;; also be moved into the backends. It stays for now, however, since +;; it is used in code below. (defun vc-trunk-p (rev) "Return t if REV is a revision on the trunk." (not (eq nil (string-match "\\`[0-9]+\\.[0-9]+\\'" rev)))) @@ -717,7 +697,7 @@ SETTINGS is a list of two-element lists, each of which has the (or (eq (vc-checkout-model file) 'implicit) (memq (vc-state file) '(edited needs-merge)))) -;;; Two macros for elisp programming +;; Two macros for elisp programming ;;;###autoload (defmacro with-vc-file (file comment &rest body) "Check out a writable copy of FILE if necessary and execute the body. @@ -1265,7 +1245,7 @@ merge in the changes into your working copy." (vc-next-action-on-file buffer-file-name verbose) (error "Buffer %s is not associated with a file" (buffer-name))))) -;;; These functions help the vc-next-action entry point +;; These functions help the vc-next-action entry point ;;;###autoload (defun vc-register (&optional set-version comment) @@ -2033,12 +2013,9 @@ The conflicts must be marked with rcsmerge conflict markers." (defvar vc-dired-mode-map (let ((map (make-sparse-keymap)) (vmap (make-sparse-keymap))) - (define-key map "\C-xv" vc-prefix-map) - ;; Emacs-20 has a lousy keymap inheritance that won't work here. - ;; Emacs-21's is still lousy but just better enough that it'd work. -sm - ;; (set-keymap-parent vmap vc-prefix-map) - (setq vmap vc-prefix-map) + (define-key map "\C-xv" vmap) (define-key map "v" vmap) + (set-keymap-parent vmap vc-prefix-map) (define-key vmap "t" 'vc-dired-toggle-terse-mode) map)) @@ -2790,7 +2767,7 @@ Uses `rcs2log' which only works for RCS and CVS." (setq default-directory (file-name-directory changelog)) (delete-file tempfile))))) -;;; Annotate functionality +;; Annotate functionality ;; Declare globally instead of additional parameter to ;; temp-buffer-show-function (not possible to pass more than one @@ -3076,7 +3053,7 @@ If `log-edit' is not available, resort to `vc-log-mode'." (set-buffer-modified-p nil) (setq buffer-file-name nil)) -;;; These things should probably be generally available +;; These things should probably be generally available (defun vc-file-tree-walk (dirname func &rest args) "Walk recursively through DIRNAME. @@ -3102,350 +3079,353 @@ Invoke FUNC f ARGS on each VC-managed file f underneath it." (provide 'vc) -;;; DEVELOPER'S NOTES ON CONCURRENCY PROBLEMS IN THIS CODE -;;; -;;; These may be useful to anyone who has to debug or extend the package. -;;; (Note that this information corresponds to versions 5.x. Some of it -;;; might have been invalidated by the additions to support branching -;;; and RCS keyword lookup. AS, 1995/03/24) -;;; -;;; A fundamental problem in VC is that there are time windows between -;;; vc-next-action's computations of the file's version-control state and -;;; the actions that change it. This is a window open to lossage in a -;;; multi-user environment; someone else could nip in and change the state -;;; of the master during it. -;;; -;;; The performance problem is that rlog/prs calls are very expensive; we want -;;; to avoid them as much as possible. -;;; -;;; ANALYSIS: -;;; -;;; 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 -;;; master. -;;; -;;; The race condition implies that we have to either (a) lock the master -;;; during the entire execution of vc-next-action, or (b) detect and -;;; recover from errors resulting from dispatch on an out-of-date state. -;;; -;;; Alternative (a) appears to be infeasible. The problem is that we can't -;;; guarantee that the lock will ever be removed. Suppose a user starts a -;;; checkin, the change message buffer pops up, and the user, having wandered -;;; off to do something else, simply forgets about it? -;;; -;;; Alternative (b), on the other hand, works well with a cheap way to speed up -;;; vc-state. Usually, if a file is registered, we can read its locked/ -;;; unlocked state and its current owner from its permissions. -;;; -;;; This shortcut will fail if someone has manually changed the workfile's -;;; permissions; also if developers are munging the workfile in several -;;; directories, with symlinks to a master (in this latter case, the -;;; permissions shortcut will fail to detect a lock asserted from another -;;; directory). -;;; -;;; Note that these cases correspond exactly to the errors which could happen -;;; because of a competing checkin/checkout race in between two instances of -;;; vc-next-action. -;;; -;;; For VC's purposes, a workfile/master pair may have the following states: -;;; -;;; A. Unregistered. There is a workfile, there is no master. -;;; -;;; B. Registered and not locked by anyone. -;;; -;;; C. Locked by calling user and unchanged. -;;; -;;; D. Locked by the calling user and changed. -;;; -;;; E. Locked by someone other than the calling user. -;;; -;;; This makes for 25 states and 20 error conditions. Here's the matrix: -;;; -;;; VC's idea of state -;;; | -;;; V Actual state RCS action SCCS action Effect -;;; A B C D E -;;; A . 1 2 3 4 ci -u -t- admin -fb -i initial admin -;;; B 5 . 6 7 8 co -l get -e checkout -;;; C 9 10 . 11 12 co -u unget; get revert -;;; D 13 14 15 . 16 ci -u -m delta -y; get checkin -;;; E 17 18 19 20 . rcs -u -M -l unget -n ; get -g steal lock -;;; -;;; All commands take the master file name as a last argument (not shown). -;;; -;;; In the discussion below, a "self-race" is a pathological situation in -;;; which VC operations are being attempted simultaneously by two or more -;;; Emacsen running under the same username. -;;; -;;; The vc-next-action code has the following windows: -;;; -;;; Window P: -;;; Between the check for existence of a master file and the call to -;;; admin/checkin in vc-buffer-admin (apparent state A). This window may -;;; never close if the initial-comment feature is on. -;;; -;;; Window Q: -;;; Between the call to vc-workfile-unchanged-p in and the immediately -;;; following revert (apparent state C). -;;; -;;; Window R: -;;; Between the call to vc-workfile-unchanged-p in and the following -;;; checkin (apparent state D). This window may never close. -;;; -;;; Window S: -;;; Between the unlock and the immediately following checkout during a -;;; revert operation (apparent state C). Included in window Q. -;;; -;;; Window T: -;;; Between vc-state and the following checkout (apparent state B). -;;; -;;; Window U: -;;; Between vc-state and the following revert (apparent state C). -;;; Includes windows Q and S. -;;; -;;; Window V: -;;; Between vc-state and the following checkin (apparent state -;;; D). This window may never be closed if the user fails to complete the -;;; checkin message. Includes window R. -;;; -;;; Window W: -;;; Between vc-state and the following steal-lock (apparent -;;; state E). This window may never close if the user fails to complete -;;; the steal-lock message. Includes window X. -;;; -;;; Window X: -;;; Between the unlock and the immediately following re-lock during a -;;; steal-lock operation (apparent state E). This window may never close -;;; if the user fails to complete the steal-lock message. -;;; -;;; Errors: -;;; -;;; Apparent state A --- -;;; -;;; 1. File looked unregistered but is actually registered and not locked. -;;; -;;; Potential cause: someone else's admin during window P, with -;;; caller's admin happening before their checkout. -;;; -;;; RCS: Prior to version 5.6.4, ci fails with message -;;; "no lock set by ". From 5.6.4 onwards, VC uses the new -;;; ci -i option and the message is ",v: already exists". -;;; SCCS: admin will fail with error (ad19). -;;; -;;; We can let these errors be passed up to the user. -;;; -;;; 2. File looked unregistered but is actually locked by caller, unchanged. -;;; -;;; Potential cause: self-race during window P. -;;; -;;; RCS: Prior to version 5.6.4, reverts the file to the last saved -;;; version and unlocks it. From 5.6.4 onwards, VC uses the new -;;; ci -i option, failing with message ",v: already exists". -;;; SCCS: will fail with error (ad19). -;;; -;;; Either of these consequences is acceptable. -;;; -;;; 3. File looked unregistered but is actually locked by caller, changed. -;;; -;;; Potential cause: self-race during window P. -;;; -;;; RCS: Prior to version 5.6.4, VC registers the caller's workfile as -;;; a delta with a null change comment (the -t- switch will be -;;; ignored). From 5.6.4 onwards, VC uses the new ci -i option, -;;; failing with message ",v: already exists". -;;; SCCS: will fail with error (ad19). -;;; -;;; 4. File looked unregistered but is locked by someone else. -;;; -;;; Potential cause: someone else's admin during window P, with -;;; caller's admin happening *after* their checkout. -;;; -;;; RCS: Prior to version 5.6.4, ci fails with a -;;; "no lock set by " message. From 5.6.4 onwards, -;;; VC uses the new ci -i option, failing with message -;;; ",v: already exists". -;;; SCCS: will fail with error (ad19). -;;; -;;; We can let these errors be passed up to the user. -;;; -;;; Apparent state B --- -;;; -;;; 5. File looked registered and not locked, but is actually unregistered. -;;; -;;; Potential cause: master file got nuked during window P. -;;; -;;; RCS: will fail with "RCS/: No such file or directory" -;;; SCCS: will fail with error ut4. -;;; -;;; We can let these errors be passed up to the user. -;;; -;;; 6. File looked registered and not locked, but is actually locked by the -;;; calling user and unchanged. -;;; -;;; Potential cause: self-race during window T. -;;; -;;; RCS: in the same directory as the previous workfile, co -l will fail -;;; with "co error: writable foo exists; checkout aborted". In any other -;;; directory, checkout will succeed. -;;; SCCS: will fail with ge17. -;;; -;;; Either of these consequences is acceptable. -;;; -;;; 7. File looked registered and not locked, but is actually locked by the -;;; calling user and changed. -;;; -;;; As case 6. -;;; -;;; 8. File looked registered and not locked, but is actually locked by another -;;; user. -;;; -;;; Potential cause: someone else checks it out during window T. -;;; -;;; RCS: co error: revision 1.3 already locked by -;;; SCCS: fails with ge4 (in directory) or ut7 (outside it). -;;; -;;; We can let these errors be passed up to the user. -;;; -;;; Apparent state C --- -;;; -;;; 9. File looks locked by calling user and unchanged, but is unregistered. -;;; -;;; As case 5. -;;; -;;; 10. File looks locked by calling user and unchanged, but is actually not -;;; locked. -;;; -;;; Potential cause: a self-race in window U, or by the revert's -;;; landing during window X of some other user's steal-lock or window S -;;; of another user's revert. -;;; -;;; RCS: succeeds, refreshing the file from the identical version in -;;; the master. -;;; SCCS: fails with error ut4 (p file nonexistent). -;;; -;;; Either of these consequences is acceptable. -;;; -;;; 11. File is locked by calling user. It looks unchanged, but is actually -;;; changed. -;;; -;;; Potential cause: the file would have to be touched by a self-race -;;; during window Q. -;;; -;;; The revert will succeed, removing whatever changes came with -;;; the touch. It is theoretically possible that work could be lost. -;;; -;;; 12. File looks like it's locked by the calling user and unchanged, but -;;; it's actually locked by someone else. -;;; -;;; Potential cause: a steal-lock in window V. -;;; -;;; RCS: co error: revision locked by ; use co -r or rcs -u -;;; SCCS: fails with error un2 -;;; -;;; We can pass these errors up to the user. -;;; -;;; Apparent state D --- -;;; -;;; 13. File looks like it's locked by the calling user and changed, but it's -;;; actually unregistered. -;;; -;;; Potential cause: master file got nuked during window P. -;;; -;;; RCS: Prior to version 5.6.4, checks in the user's version as an -;;; initial delta. From 5.6.4 onwards, VC uses the new ci -j -;;; option, failing with message "no such file or directory". -;;; SCCS: will fail with error ut4. -;;; -;;; This case is kind of nasty. Under RCS prior to version 5.6.4, -;;; VC may fail to detect the loss of previous version information. -;;; -;;; 14. File looks like it's locked by the calling user and changed, but it's -;;; actually unlocked. -;;; -;;; Potential cause: self-race in window V, or the checkin happening -;;; during the window X of someone else's steal-lock or window S of -;;; someone else's revert. -;;; -;;; RCS: ci will fail with "no lock set by ". -;;; SCCS: delta will fail with error ut4. -;;; -;;; 15. File looks like it's locked by the calling user and changed, but it's -;;; actually locked by the calling user and unchanged. -;;; -;;; Potential cause: another self-race --- a whole checkin/checkout -;;; sequence by the calling user would have to land in window R. -;;; -;;; SCCS: checks in a redundant delta and leaves the file unlocked as usual. -;;; RCS: reverts to the file state as of the second user's checkin, leaving -;;; the file unlocked. -;;; -;;; It is theoretically possible that work could be lost under RCS. -;;; -;;; 16. File looks like it's locked by the calling user and changed, but it's -;;; actually locked by a different user. -;;; -;;; RCS: ci error: no lock set by -;;; SCCS: unget will fail with error un2 -;;; -;;; We can pass these errors up to the user. -;;; -;;; Apparent state E --- -;;; -;;; 17. File looks like it's locked by some other user, but it's actually -;;; unregistered. -;;; -;;; As case 13. -;;; -;;; 18. File looks like it's locked by some other user, but it's actually -;;; unlocked. -;;; -;;; Potential cause: someone released a lock during window W. -;;; -;;; RCS: The calling user will get the lock on the file. -;;; SCCS: unget -n will fail with cm4. -;;; -;;; Either of these consequences will be OK. -;;; -;;; 19. File looks like it's locked by some other user, but it's actually -;;; locked by the calling user and unchanged. -;;; -;;; Potential cause: the other user relinquishing a lock followed by -;;; a self-race, both in window W. -;;; -;;; Under both RCS and SCCS, both unlock and lock will succeed, making -;;; the sequence a no-op. -;;; -;;; 20. File looks like it's locked by some other user, but it's actually -;;; locked by the calling user and changed. -;;; -;;; As case 19. -;;; -;;; PROBLEM CASES: -;;; -;;; In order of decreasing severity: -;;; -;;; Cases 11 and 15 are the only ones that potentially lose work. -;;; They would require a self-race for this to happen. -;;; -;;; Case 13 in RCS loses information about previous deltas, retaining -;;; only the information in the current workfile. This can only happen -;;; if the master file gets nuked in window P. -;;; -;;; Case 3 in RCS and case 15 under SCCS insert a redundant delta with -;;; no change comment in the master. This would require a self-race in -;;; window P or R respectively. -;;; -;;; Cases 2, 10, 19 and 20 do extra work, but make no changes. -;;; -;;; Unfortunately, it appears to me that no recovery is possible in these -;;; cases. They don't yield error messages, so there's no way to tell that -;;; a race condition has occurred. -;;; -;;; All other cases don't change either the workfile or the master, and -;;; trigger command errors which the user will see. +;; DEVELOPER'S NOTES ON CONCURRENCY PROBLEMS IN THIS CODE +;; +;; This is actually seriously out-of-date because the code has changed +;; a fair bit since then. -stef +;; +;; These may be useful to anyone who has to debug or extend the package. +;; (Note that this information corresponds to versions 5.x. Some of it +;; might have been invalidated by the additions to support branching +;; and RCS keyword lookup. AS, 1995/03/24) +;; +;; A fundamental problem in VC is that there are time windows between +;; vc-next-action's computations of the file's version-control state and +;; the actions that change it. This is a window open to lossage in a +;; multi-user environment; someone else could nip in and change the state +;; of the master during it. +;; +;; The performance problem is that rlog/prs calls are very expensive; we want +;; to avoid them as much as possible. +;; +;; ANALYSIS: +;; +;; 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 +;; master. +;; +;; The race condition implies that we have to either (a) lock the master +;; during the entire execution of vc-next-action, or (b) detect and +;; recover from errors resulting from dispatch on an out-of-date state. +;; +;; Alternative (a) appears to be infeasible. The problem is that we can't +;; guarantee that the lock will ever be removed. Suppose a user starts a +;; checkin, the change message buffer pops up, and the user, having wandered +;; off to do something else, simply forgets about it? +;; +;; Alternative (b), on the other hand, works well with a cheap way to speed up +;; vc-state. Usually, if a file is registered, we can read its locked/ +;; unlocked state and its current owner from its permissions. +;; +;; This shortcut will fail if someone has manually changed the workfile's +;; permissions; also if developers are munging the workfile in several +;; directories, with symlinks to a master (in this latter case, the +;; permissions shortcut will fail to detect a lock asserted from another +;; directory). +;; +;; Note that these cases correspond exactly to the errors which could happen +;; because of a competing checkin/checkout race in between two instances of +;; vc-next-action. +;; +;; For VC's purposes, a workfile/master pair may have the following states: +;; +;; A. Unregistered. There is a workfile, there is no master. +;; +;; B. Registered and not locked by anyone. +;; +;; C. Locked by calling user and unchanged. +;; +;; D. Locked by the calling user and changed. +;; +;; E. Locked by someone other than the calling user. +;; +;; This makes for 25 states and 20 error conditions. Here's the matrix: +;; +;; VC's idea of state +;; | +;; V Actual state RCS action SCCS action Effect +;; A B C D E +;; A . 1 2 3 4 ci -u -t- admin -fb -i initial admin +;; B 5 . 6 7 8 co -l get -e checkout +;; C 9 10 . 11 12 co -u unget; get revert +;; D 13 14 15 . 16 ci -u -m delta -y; get checkin +;; E 17 18 19 20 . rcs -u -M -l unget -n ; get -g steal lock +;; +;; All commands take the master file name as a last argument (not shown). +;; +;; In the discussion below, a "self-race" is a pathological situation in +;; which VC operations are being attempted simultaneously by two or more +;; Emacsen running under the same username. +;; +;; The vc-next-action code has the following windows: +;; +;; Window P: +;; Between the check for existence of a master file and the call to +;; admin/checkin in vc-buffer-admin (apparent state A). This window may +;; never close if the initial-comment feature is on. +;; +;; Window Q: +;; Between the call to vc-workfile-unchanged-p in and the immediately +;; following revert (apparent state C). +;; +;; Window R: +;; Between the call to vc-workfile-unchanged-p in and the following +;; checkin (apparent state D). This window may never close. +;; +;; Window S: +;; Between the unlock and the immediately following checkout during a +;; revert operation (apparent state C). Included in window Q. +;; +;; Window T: +;; Between vc-state and the following checkout (apparent state B). +;; +;; Window U: +;; Between vc-state and the following revert (apparent state C). +;; Includes windows Q and S. +;; +;; Window V: +;; Between vc-state and the following checkin (apparent state +;; D). This window may never be closed if the user fails to complete the +;; checkin message. Includes window R. +;; +;; Window W: +;; Between vc-state and the following steal-lock (apparent +;; state E). This window may never close if the user fails to complete +;; the steal-lock message. Includes window X. +;; +;; Window X: +;; Between the unlock and the immediately following re-lock during a +;; steal-lock operation (apparent state E). This window may never close +;; if the user fails to complete the steal-lock message. +;; +;; Errors: +;; +;; Apparent state A --- +;; +;; 1. File looked unregistered but is actually registered and not locked. +;; +;; Potential cause: someone else's admin during window P, with +;; caller's admin happening before their checkout. +;; +;; RCS: Prior to version 5.6.4, ci fails with message +;; "no lock set by ". From 5.6.4 onwards, VC uses the new +;; ci -i option and the message is ",v: already exists". +;; SCCS: admin will fail with error (ad19). +;; +;; We can let these errors be passed up to the user. +;; +;; 2. File looked unregistered but is actually locked by caller, unchanged. +;; +;; Potential cause: self-race during window P. +;; +;; RCS: Prior to version 5.6.4, reverts the file to the last saved +;; version and unlocks it. From 5.6.4 onwards, VC uses the new +;; ci -i option, failing with message ",v: already exists". +;; SCCS: will fail with error (ad19). +;; +;; Either of these consequences is acceptable. +;; +;; 3. File looked unregistered but is actually locked by caller, changed. +;; +;; Potential cause: self-race during window P. +;; +;; RCS: Prior to version 5.6.4, VC registers the caller's workfile as +;; a delta with a null change comment (the -t- switch will be +;; ignored). From 5.6.4 onwards, VC uses the new ci -i option, +;; failing with message ",v: already exists". +;; SCCS: will fail with error (ad19). +;; +;; 4. File looked unregistered but is locked by someone else. ;;; -;;; Thus, there is no explicit recovery code. +;; Potential cause: someone else's admin during window P, with +;; caller's admin happening *after* their checkout. +;; +;; RCS: Prior to version 5.6.4, ci fails with a +;; "no lock set by " message. From 5.6.4 onwards, +;; VC uses the new ci -i option, failing with message +;; ",v: already exists". +;; SCCS: will fail with error (ad19). +;; +;; We can let these errors be passed up to the user. +;; +;; Apparent state B --- +;; +;; 5. File looked registered and not locked, but is actually unregistered. +;; +;; Potential cause: master file got nuked during window P. +;; +;; RCS: will fail with "RCS/: No such file or directory" +;; SCCS: will fail with error ut4. +;; +;; We can let these errors be passed up to the user. +;; +;; 6. File looked registered and not locked, but is actually locked by the +;; calling user and unchanged. +;; +;; Potential cause: self-race during window T. +;; +;; RCS: in the same directory as the previous workfile, co -l will fail +;; with "co error: writable foo exists; checkout aborted". In any other +;; directory, checkout will succeed. +;; SCCS: will fail with ge17. +;; +;; Either of these consequences is acceptable. +;; +;; 7. File looked registered and not locked, but is actually locked by the +;; calling user and changed. +;; +;; As case 6. +;; +;; 8. File looked registered and not locked, but is actually locked by another +;; user. +;; +;; Potential cause: someone else checks it out during window T. +;; +;; RCS: co error: revision 1.3 already locked by +;; SCCS: fails with ge4 (in directory) or ut7 (outside it). +;; +;; We can let these errors be passed up to the user. +;; +;; Apparent state C --- +;; +;; 9. File looks locked by calling user and unchanged, but is unregistered. +;; +;; As case 5. +;; +;; 10. File looks locked by calling user and unchanged, but is actually not +;; locked. +;; +;; Potential cause: a self-race in window U, or by the revert's +;; landing during window X of some other user's steal-lock or window S +;; of another user's revert. +;; +;; RCS: succeeds, refreshing the file from the identical version in +;; the master. +;; SCCS: fails with error ut4 (p file nonexistent). +;; +;; Either of these consequences is acceptable. +;; +;; 11. File is locked by calling user. It looks unchanged, but is actually +;; changed. +;; +;; Potential cause: the file would have to be touched by a self-race +;; during window Q. +;; +;; The revert will succeed, removing whatever changes came with +;; the touch. It is theoretically possible that work could be lost. +;; +;; 12. File looks like it's locked by the calling user and unchanged, but +;; it's actually locked by someone else. +;; +;; Potential cause: a steal-lock in window V. +;; +;; RCS: co error: revision locked by ; use co -r or rcs -u +;; SCCS: fails with error un2 +;; +;; We can pass these errors up to the user. +;; +;; Apparent state D --- +;; +;; 13. File looks like it's locked by the calling user and changed, but it's +;; actually unregistered. +;; +;; Potential cause: master file got nuked during window P. +;; +;; RCS: Prior to version 5.6.4, checks in the user's version as an +;; initial delta. From 5.6.4 onwards, VC uses the new ci -j +;; option, failing with message "no such file or directory". +;; SCCS: will fail with error ut4. +;; +;; This case is kind of nasty. Under RCS prior to version 5.6.4, +;; VC may fail to detect the loss of previous version information. +;; +;; 14. File looks like it's locked by the calling user and changed, but it's +;; actually unlocked. +;; +;; Potential cause: self-race in window V, or the checkin happening +;; during the window X of someone else's steal-lock or window S of +;; someone else's revert. +;; +;; RCS: ci will fail with "no lock set by ". +;; SCCS: delta will fail with error ut4. +;; +;; 15. File looks like it's locked by the calling user and changed, but it's +;; actually locked by the calling user and unchanged. +;; +;; Potential cause: another self-race --- a whole checkin/checkout +;; sequence by the calling user would have to land in window R. +;; +;; SCCS: checks in a redundant delta and leaves the file unlocked as usual. +;; RCS: reverts to the file state as of the second user's checkin, leaving +;; the file unlocked. +;; +;; It is theoretically possible that work could be lost under RCS. +;; +;; 16. File looks like it's locked by the calling user and changed, but it's +;; actually locked by a different user. +;; +;; RCS: ci error: no lock set by +;; SCCS: unget will fail with error un2 +;; +;; We can pass these errors up to the user. +;; +;; Apparent state E --- +;; +;; 17. File looks like it's locked by some other user, but it's actually +;; unregistered. +;; +;; As case 13. +;; +;; 18. File looks like it's locked by some other user, but it's actually +;; unlocked. +;; +;; Potential cause: someone released a lock during window W. +;; +;; RCS: The calling user will get the lock on the file. +;; SCCS: unget -n will fail with cm4. +;; +;; Either of these consequences will be OK. +;; +;; 19. File looks like it's locked by some other user, but it's actually +;; locked by the calling user and unchanged. +;; +;; Potential cause: the other user relinquishing a lock followed by +;; a self-race, both in window W. +;; +;; Under both RCS and SCCS, both unlock and lock will succeed, making +;; the sequence a no-op. +;; +;; 20. File looks like it's locked by some other user, but it's actually +;; locked by the calling user and changed. +;; +;; As case 19. +;; +;; PROBLEM CASES: +;; +;; In order of decreasing severity: +;; +;; Cases 11 and 15 are the only ones that potentially lose work. +;; They would require a self-race for this to happen. +;; +;; Case 13 in RCS loses information about previous deltas, retaining +;; only the information in the current workfile. This can only happen +;; if the master file gets nuked in window P. +;; +;; Case 3 in RCS and case 15 under SCCS insert a redundant delta with +;; no change comment in the master. This would require a self-race in +;; window P or R respectively. +;; +;; Cases 2, 10, 19 and 20 do extra work, but make no changes. +;; +;; Unfortunately, it appears to me that no recovery is possible in these +;; cases. They don't yield error messages, so there's no way to tell that +;; a race condition has occurred. +;; +;; All other cases don't change either the workfile or the master, and +;; trigger command errors which the user will see. +;; +;; Thus, there is no explicit recovery code. ;;; vc.el ends here -- 2.39.2