Don't abort when backup files already exist. Don't allow alternative names.

Rationale:
- When the user wants to revert, he shouldn't be stopped from doing
  this just because some old backups will be overwritten.
- To not clobber important files by accident, alternative names for backup
  files were disabled. As the backup target now has a fixed name, the user
  doesn't have to be informed about the backup copy (unless --verbose)

mercurial/commands.py

@@ -2287,9 +2287,8 b' def revert(ui, repo, *pats, **opts):'
     to the named files or directories.  This restores the contents of
     the affected files to an unmodified state.
 
-    Modified files have backup copies saved before revert.  To disable
-    backups, use --no-backup.  To change the name of backup files, use
-    --backup to give a format string.
+    Modified files are saved with a .orig suffix before reverting.
+    To disable these backups, use --no-backup.
 
     Using the -r option, it reverts the given files or directories to
     their state as of an earlier revision.  This can be helpful to "roll
@@ -2309,24 +2308,6 b' def revert(ui, repo, *pats, **opts):'
     node = opts['rev'] and repo.lookup(opts['rev']) or parent
     mf = repo.manifest.read(repo.changelog.read(node)[0])
 
-    def backup(name, exact):
-        bakname = make_filename(repo, repo.changelog,
-                                opts['backup_name'] or '%p.orig',
-                                node=parent, pathname=name)
-        if os.path.exists(name):
-            # if backup already exists and is same as backup we want
-            # to make, do nothing
-            if os.path.exists(bakname):
-                if repo.wread(name) == repo.wread(bakname):
-                    return
-                raise util.Abort(_('cannot save current version of %s - '
-                                   '%s exists and differs') %
-                                 (name, bakname))
-            ui.status(('saving current version of %s as %s\n') %
-                      (name, bakname))
-            shutil.copyfile(name, bakname)
-            shutil.copymode(name, bakname)
-
     wlock = repo.wlock()
 
     entries = []
@@ -2362,8 +2343,12 b' def revert(ui, repo, *pats, **opts):'
     for abs, rel, exact in entries:
         def handle(xlist, dobackup):
             xlist[0].append(abs)
-            if dobackup and not opts['no_backup']:
-                backup(rel, exact)
+            if dobackup and not opts['no_backup'] and os.path.exists(rel):
+                bakname = "%s.orig" % rel
+                ui.note(_('saving current version of %s as %s\n') %
+                        (rel, bakname))
+                shutil.copyfile(rel, bakname)
+                shutil.copymode(rel, bakname)
             if ui.verbose or not exact:
                 ui.status(xlist[1] % rel)
         for table, hitlist, misslist, backuphit, backupmiss in disptable:
@@ -3011,7 +2996,6 b' table = {'
     "^revert":
         (revert,
          [('r', 'rev', '', _('revision to revert to')),
-          ('', 'backup-name', '', _('save backup with formatted name')),
           ('', 'no-backup', None, _('do not save backup copies of files')),
           ('I', 'include', [], _('include names matching given patterns')),
           ('X', 'exclude', [], _('exclude names matching given patterns'))],

tests/test-confused-revert.out

@@ -2,7 +2,6 b''
 A b
 R a
 reverting...
-saving current version of b as b.orig
 forgetting b
 undeleting a
 %%% should show b unknown and a back to normal

tests/test-merge-revert.out

@@ -3,7 +3,6 b' 0:eb43f19ff115'
 016807e6fdaf tip
 eb43f19ff115
 eb43f19ff115+
-saving current version of file1 as file1.orig
 reverting file1
 ? file1.orig
 eb43f19ff115

tests/test-revert

@@ -22,16 +22,16 b' hg revert a'
 echo %% should show b added, copy saved, and c modified
 hg status
 hg revert b
-echo %% should show b unknown, b.bak unknown, and c modified
+echo %% should show b unknown, b.orig unknown, and c modified
 hg status
 hg revert --no-backup c
-echo %% should show unknown: b b.bak
+echo %% should show unknown: b b.orig
 hg status
-echo %% should show a b b.bak c e
+echo %% should show a b b.orig c e
 ls
-echo %% should save backup to e.0
+echo %% should verbosely save backup to e.orig
 echo z > e
-hg revert --backup='%p.%R'
+hg revert -v
 echo %% should say no changes needed
 hg revert a
 echo %% should say file not managed

tests/test-revert.out

@@ -13,23 +13,25 b' R a'
 %% should show b added, copy saved, and c modified
 M c
 A b
-saving current version of b as b.orig
-%% should show b unknown, b.bak unknown, and c modified
+%% should show b unknown, b.orig unknown, and c modified
 M c
 ? b
 ? b.orig
-%% should show unknown: b b.bak
+%% should show unknown: b b.orig
 ? b
 ? b.orig
-%% should show a b b.bak c e
+%% should show a b b.orig c e
 a
 b
 b.orig
 c
 e
-%% should save backup to e.0
-saving current version of e as e.0
+%% should verbosely save backup to e.orig
+saving current version of e as e.orig
 reverting e
+resolving manifests
+getting e
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 %% should say no changes needed
 no changes needed to a
 %% should say file not managed

tests/test-tag.out

@@ -21,7 +21,6 b' failed'
 use of 'hg tag NAME [REV]' is deprecated, please use 'hg tag [-r REV] NAME' instead
 abort: use only one form to specify the revision
 failed
-saving current version of .hgtags as .hgtags.orig
 use of 'hg tag NAME [REV]' is deprecated, please use 'hg tag [-r REV] NAME' instead
 0acdaf8983679e0aac16e811534eb49d7ee1f2b4 bleah
 0acdaf8983679e0aac16e811534eb49d7ee1f2b4 bleah0